## 20001

20001^{2} = 400040001 is a reversible square (100040004 = 10002^{2}).

20001^{2} = 400040001 is a square consisting of 3 kinds of digits.

by Yoshio Mimura, Kobe, Japan

## 20002

20002^{2} = 400080004 is a palindromic square.

20002^{2} = 400080004 is a square consisting of 3 kinds of even digits.

by Yoshio Mimura, Kobe, Japan

## 20010

20010^{2} = (13^{2} + 5)(15^{2} + 5)(100^{2} + 5).

by Yoshio Mimura, Kobe, Japan

## 20011

20011^{2} = 400440121 is a reversible square (121044004 = 11002^{2}).

by Yoshio Mimura, Kobe, Japan

## 20012

20012^{2} = 400480144 is a reverdible square (441084004 = 21002^{2}).

by Yoshio Mimura, Kobe, Japan

## 20021

20021^{2} = 400840441 is a reversible square (144048004 = 12002^{2}).

by Yoshio Mimura, Kobe, Japan

## 20022

20022^{2}± 5 are primes.

20022^{2} = 400880484 is a reversible square (484088044 = 22002^{2}).

20022^{2} = 400880484 is a square consisting of 3 kinds of even digits.

by Yoshio Mimura, Kobe, Japan

## 20044

20044^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20056

20056^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20064

20064^{2} = (4^{2} + 8)(6^{2} + 8)(12^{2} + 8)(50^{2} + 8).

185^{2} + 20064 = 233^{2}, 185^{2} - 20064 = 119^{2}.

by Yoshio Mimura, Kobe, Japan

## 20079

20079^{2} = 1344^{2} + 1345^{2} + 1346^{2} + ... + 1537^{2}.

by Yoshio Mimura, Kobe, Japan

## 20089

20089^{2} = 403567921 is a square consisting of different digits.

by Yoshio Mimura, Kobe, Japan

## 20100

20100^{2} = (1^{3} + 9)(5^{3} + 9)(6^{3} + 9)(11^{3} + 9).

by Yoshio Mimura, Kobe, Japan

## 20101

20101^{2} = 404050201 is a reversible square (102050404 = 10102^{2}).

20101^{2} = 404050201, and 44521 = 211^{2}.

by Yoshio Mimura, Kobe, Japan

## 20102

20102^{2} = 404090404 is a palindromic square consisting of 3 kinds of digits.

20102^{2} = 404090404, and 44944 = 212^{2}.

by Yoshio Mimura, Kobe, Japan

## 20111

20111^{2} = 404452321 is a reversible square (123254404 = 11102^{2}).

by Yoshio Mimura, Kobe, Japan

## 20112

20112^{2} = 404492544 is a reversible square (445294404 = 21102^{2}).

by Yoshio Mimura, Kobe, Japan

## 20121

20121^{2} = 404854641 is a reversible square (146458404 = 12102^{2}).

by Yoshio Mimura, Kobe, Japan

## 20122

20122^{2} = 404894884 is a reversible square (488498404 = 22102^{2}).

by Yoshio Mimura, Kobe, Japan

## 20124

20124^{2}± 5 are primes.

by Yoshio Mimura, Kobe, Japan

## 20126

20126^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20152

20152^{2} = 3492^{2} + 3493^{2} + 3494^{2} + ... + 3524^{2}.

by Yoshio Mimura, Kobe, Japan

## 20160

20160^{2} = (11^{2} - 1)(19^{2} - 1)(97^{2} - 1) = (15^{2} - 1)(19^{2} - 1)(71^{2} - 1) = (17^{2} - 1)(29^{2} - 1)(41^{2} - 1)

= (2^{2} - 1)(11^{2} - 1)(15^{2} - 1)(71^{2} - 1) = (2^{2} - 1)(13^{2} - 1)(29^{2} - 1)(31^{2} - 1)

= (2^{2} - 1)(15^{2} - 1)(19^{2} - 1)(41^{2} - 1) = (2^{2} - 1)(3^{2} - 1)(11^{2} - 1)(13^{2} - 1)(29^{2} - 1)

= (2^{2} - 1)(3^{2} - 1)(4^{2} - 1)(11^{2} - 1)(97^{2} - 1) = (2^{2} - 1)(3^{2} - 1)(4^{2} - 1)(15^{2} - 1)(71^{2} - 1)

= (2^{2} - 1)(3^{2} - 1)(4^{2} - 1)(8^{2} - 1)(9^{2} - 1)(15^{2} - 1)

= (2^{2} - 1)(3^{2} - 1)(5^{2} - 1)(6^{2} - 1)(11^{2} - 1)(13^{2} - 1)

= (2^{2} - 1)(3^{2} - 1)(6^{2} - 1)(17^{2} - 1)(41^{2} - 1) = (2^{2} - 1)(4^{2} - 1)(31^{2} - 1)(97^{2} - 1)

= (2^{2} - 1)(4^{2} - 1)(5^{2} - 1)(15^{2} - 1)(41^{2} - 1)

= (2^{2} - 1)(4^{2} - 1)(5^{2} - 1)(6^{2} - 1)(7^{2} - 1)(15^{2} - 1)

= (2^{2} - 1)(4^{2} - 1)(7^{2} - 1)(15^{2} - 1)(29^{2} - 1) = (2^{2} - 1)(5^{2} - 1)(6^{2} - 1)(13^{2} - 1)(31^{2} - 1)

= (2^{2} - 1)(6^{2} - 1)(7^{2} - 1)(15^{2} - 1)(19^{2} - 1) = (2^{2} - 1)(6^{2} - 1)(9^{2} - 1)(13^{2} - 1)(17^{2} - 1)

= (2^{2} - 1)(7^{2} - 1)(17^{2} - 1)(99^{2} - 1) = (2^{2} - 1)(8^{2} - 1)(9^{2} - 1)(11^{2} - 1)(15^{2} - 1)

= (3^{2} - 1)(13^{2} - 1)(19^{2} - 1)(29^{2} - 1) = (3^{2} - 1)(4^{2} - 1)(19^{2} - 1)(97^{2} - 1)

= (3^{2} - 1)(4^{2} - 1)(5^{2} - 1)(13^{2} - 1)(29^{2} - 1) = (3^{2} - 1)(5^{2} - 1)(6^{2} - 1)(13^{2} - 1)(19^{2} - 1)

= (3^{2} - 1)(5^{2} - 1)(6^{2} - 1)(8^{2} - 1)(31^{2} - 1) = (3^{2} - 1)(6^{2} - 1)(17^{2} - 1)(71^{2} - 1)

= (3^{2} - 1)(6^{2} - 1)(8^{2} - 1)(9^{2} - 1)(17^{2} - 1) = (3^{2} - 1)(8^{2} - 1)(29^{2} - 1)(31^{2} - 1)

= (4^{2} - 1)(41^{2} - 1)(127^{2} - 1) = (4^{2} - 1)(5^{2} - 1)(11^{2} - 1)(97^{2} - 1)

= (4^{2} - 1)(5^{2} - 1)(15^{2} - 1)(71^{2} - 1) = (4^{2} - 1)(5^{2} - 1)(8^{2} - 1)(9^{2} - 1)(15^{2} - 1)

= (4^{2} - 1)(6^{2} - 1)(7^{2} - 1)(127^{2} - 1) = (5^{2} - 1)(11^{2} - 1)(13^{2} - 1)(29^{2} - 1)

= (5^{2} - 1)(6^{2} - 1)(17^{2} - 1)(41^{2} - 1) = (6^{2} - 1)(7^{2} - 1)(17^{2} - 1)(29^{2} - 1)

= (6^{2} - 1)(7^{2} - 1)(9^{2} - 1)(55^{2} - 1) = (7^{2} - 1)(41^{2} - 1)(71^{2} - 1)

= (7^{2} - 1)(8^{2} - 1)(9^{2} - 1)(41^{2} - 1) = (8^{2} - 1)(9^{2} - 1)(15^{2} - 1)(19^{2} - 1)

= (9^{2} - 1)(41^{2} - 1)(55^{2} - 1).

by Yoshio Mimura, Kobe, Japan

## 20164

20164 is a square (142^{2}) consisting of different digits.

by Yoshio Mimura, Kobe, Japan

## 20178

20178^{2} = (1^{2} + 2)(2^{2} + 2)(4756^{2} + 2) = (1^{2} + 2)(6^{2} + 2)(23^{2} + 2)(82^{2} + 2) = (4^{2} + 2)(4756^{2} + 2).

by Yoshio Mimura, Kobe, Japan

## 20184

145^{2} + 20184 = 203^{2}, 145^{2} - 20184 = 29^{2}.

by Yoshio Mimura, Kobe, Japan

## 20196

20196^{2} = (1^{2} + 2)(2^{2} + 2)(3^{2} + 2)(4^{2} + 2)(14^{2} + 2)(24^{2} + 2)

= (1^{2} + 2)(2^{2} + 2)(8^{2} + 2)(10^{2} + 2)(58^{2} + 2) = (1^{2} + 2)(4^{2} + 2)(8^{2} + 2)(14^{2} + 2)(24^{2} + 2)

= (1^{2} + 8)(2^{2} + 8)(3^{2} + 8)(5^{2} + 8)(82^{2} + 8) = (1^{2} + 8)(2^{2} + 8)(3^{2} + 8)(6^{2} + 8)(71^{2} + 8)

= (1^{2} + 8)(3^{2} + 8)(6^{2} + 8)(14^{2} + 8)(17^{2} + 8) = (1^{2} + 8)(5^{2} + 8)(14^{2} + 8)(82^{2} + 8)

= (1^{2} + 8)(6^{2} + 8)(14^{2} + 8)(71^{2} + 8) = (14^{2} + 8)(1414^{2} + 8) = (14^{2} + 8)(17^{2} + 8)(82^{2} + 8)

= (14^{2} + 8)(37^{2} + 8)(38^{2} + 8) = (2^{2} + 2)(10^{2} + 2)(14^{2} + 2)(58^{2} + 2)

= (2^{2} + 2)(3^{2} + 2)(4^{2} + 2)(10^{2} + 2)(58^{2} + 2) = (2^{2} + 2)(3^{2} + 2)(4^{2} + 2)(7^{2} + 2)(8^{2} + 2)(10^{2} + 2)

= (2^{2} + 2)(7^{2} + 2)(8^{2} + 2)(10^{2} + 2)(14^{2} + 2) = (2^{2} + 8)(3^{2} + 8)(1414^{2} + 8)

= (2^{2} + 8)(3^{2} + 8)(17^{2} + 8)(82^{2} + 8) = (2^{2} + 8)(3^{2} + 8)(37^{2} + 8)(38^{2} + 8)

= (2^{2} + 8)(3^{2} + 8)(5^{2} + 8)(14^{2} + 8)(17^{2} + 8) = (2^{2} + 8)(3^{2} + 8)(5^{2} + 8)(6^{2} + 8)(37^{2} + 8)

= (2^{2} + 8)(5^{2} + 8)(14^{2} + 8)(71^{2} + 8) = (2^{2} + 8)(71^{2} + 8)(82^{2} + 8)

= (3^{2} + 8)(5^{2} + 8)(10^{2} + 8)(82^{2} + 8) = (3^{2} + 8)(6^{2} + 8)(10^{2} + 8)(71^{2} + 8) = (38^{2} + 8)(530^{2} + 8)

= (4^{2} + 2)(8^{2} + 2)(10^{2} + 2)(58^{2} + 2) = (5^{2} + 8)(6^{2} + 8)(14^{2} + 8)(37^{2} + 8)

= (5^{2} + 8)(6^{2} + 8)(530^{2} + 8) = (6^{2} + 8)(37^{2} + 8)(82^{2} + 8).

by Yoshio Mimura, Kobe, Japan

## 20201

20201^{2} = 408080401 is a reversible square (104080804 = 10202^{2}).

20201^{2} = 408080401, and 48841 = 221^{2}.

by Yoshio Mimura, Kobe, Japan

## 20202

20202^{2} = (2^{2} + 3)(6^{2} + 3)(21^{2} + 3)(58^{2} + 3) = (3^{2} + 3)(6^{2} + 3)(16^{2} + 3)(58^{2} + 3)

= (6^{2} + 3)(16^{2} + 3)(201^{2} + 3).

by Yoshio Mimura, Kobe, Japan

## 20211

20211^{2} = 408484521 is a reversible square (125484804 = 11202^{2}).

by Yoshio Mimura, Kobe, Japan

## 20213

20213^{2} = S2(753) + S2(927), where S2(n) = 1^{2} + 2^{2} + ... + n^{2}.

by Yoshio Mimura, Kobe, Japan

## 20221

20221^{2} = 408888841 is a reversible square (148888804 = 12202^{2}).

by Yoshio Mimura, Kobe, Japan

## 20230

20230^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20240

20240^{2} = 409657600, and 4096 = 64^{2}, 57600 = 240^{2}.

by Yoshio Mimura, Kobe, Japan

## 20264

20264^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20280

13^{4} + 20280 = 221^{2}, 13^{4} - 20280 = 91^{2}.

by Yoshio Mimura, Kobe, Japan

## 20286

20286^{2} = (1^{2} + 5)(8^{2} + 5)(31^{2} + 5)(32^{2} + 5) = (1^{2} + 5)(8^{2} + 5)(997^{2} + 5)

= (17^{2} + 5)(31^{2} + 5)(38^{2} + 5) = (3^{2} + 5)(32^{2} + 5)(169^{2} + 5) = (3^{2} + 5)(4^{2} + 5)(31^{2} + 5)(38^{2} + 5)

= (3^{2} + 5)(8^{2} + 5)(17^{2} + 5)(38^{2} + 5) = (4^{2} + 5)(8^{2} + 5)(17^{2} + 5)(31^{2} + 5).

by Yoshio Mimura, Kobe, Japan

## 20295

20295^{2}± 2 are primes.

by Yoshio Mimura, Kobe, Japan

## 20300

20300^{2} = (2^{2} + 6)(8^{2} + 6)(20^{2} + 6)(38^{2} + 6).

by Yoshio Mimura, Kobe, Japan

## 20308

20308^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20314

20314^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20316

20316^{2} = 412739856 is a square consisting of different digits.

by Yoshio Mimura, Kobe, Japan

## 20318

20318^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20320

20320^{2}= 50 x 51 + 51 x 52 + 52 x 53 + ... + 1073 x 1074.

by Yoshio Mimura, Kobe, Japan

## 20329

20329^{2} = (5^{2} + 4)(3775^{2} + 4).

by Yoshio Mimura, Kobe, Japan

## 20342

20342^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20343

1^{2} + 2^{2} + ... + 20343^{2} = 2806440020084, which consists of even digits.

by Yoshio Mimura, Kobe, Japan

## 20359

20359^{2} = 414488881 is a square consisting of 3 kinds of digits.

by Yoshio Mimura, Kobe, Japan

## 20370

20370^{2} = (1^{2} + 6)(6^{2} + 6)(1188^{2} + 6) = (2^{2} + 6)(24^{2} + 6)(267^{2} + 6) = (3^{2} + 6)(24^{2} + 6)(218^{2} + 6).

by Yoshio Mimura, Kobe, Japan

## 20385

20385^{2}± 2 are primes.

by Yoshio Mimura, Kobe, Japan

## 20410

20410^{2} = (3^{2} + 4)(56^{2} + 4)(101^{2} + 4).

by Yoshio Mimura, Kobe, Japan

## 20412

20412^{2} = (1^{2} + 5)(2^{2} + 5)(3^{2} + 5)(7^{2} + 5)(101^{2} + 5) = (1^{2} + 5)(7^{2} + 5)(11^{2} + 5)(101^{2} + 5).

by Yoshio Mimura, Kobe, Japan

## 20416

20416^{2} = (13^{2} + 7)(15^{2} + 7)(101^{2} + 7) = (15^{2} + 7)(31^{2} + 7)(43^{2} + 7)

= (2^{2} + 7)(3^{2} + 7)(15^{2} + 7)(101^{2} + 7) = (2^{2} + 7)(9^{2} + 7)(15^{2} + 7)(43^{2} + 7).

by Yoshio Mimura, Kobe, Japan

## 20433

20433^{2}± 2 are primes.

by Yoshio Mimura, Kobe, Japan

## 20475

20475^{2} = (4^{2} - 1)(6^{2} - 1)(14^{2} - 1)(64^{2} - 1).

by Yoshio Mimura, Kobe, Japan

## 20484

20484^{2}± 5 are primes.

20484^{2} = 5^{3} + 91^{3} + 286^{3} + 734^{3}.

by Yoshio Mimura, Kobe, Japan

## 20496

20496^{2}± 5 are primes.

by Yoshio Mimura, Kobe, Japan

## 20500

20500^{2} = 420250000, and 4 = 2^{2}, 20250000 = 4500^{2}.

20500^{2} = (1^{2} + 1)(2^{2} + 1)(3^{2} + 1)(7^{2} + 1)(9^{2} + 1)(32^{2} + 1).

by Yoshio Mimura, Kobe, Japan

## 20502

20502^{2} = (10^{2} + 2)(2030^{2} + 2).

by Yoshio Mimura, Kobe, Japan

## 20508

20508^{2} = 420578064 is a reversible square (460875024 = 21468^{2}).

by Yoshio Mimura, Kobe, Japan

## 20513

20513^{2} = 420783169 is a sqaure consisting of different digits.

by Yoshio Mimura, Kobe, Japan

## 20521

20521^{2} = 421111441 is a square consisting of 3 kinds of digits.

by Yoshio Mimura, Kobe, Japan

## 20528

20528^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20556

20556^{2} = (1^{2} + 8)(2^{2} + 8)(1978^{2} + 8) = (10^{2} + 8)(1978^{2} + 8).

by Yoshio Mimura, Kobe, Japan

## 20558

20558^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20580

20580^{2} = (2^{2} + 6)(6^{2} + 6)(8^{2} + 6)(120^{2} + 6).

by Yoshio Mimura, Kobe, Japan

## 20587

(20587^{2} - 7) = (3^{2} - 7)(4^{2} - 7)(14^{2}2 - 7)(18^{2} - 7)(20^{2} - 7).

by Yoshio Mimura, Kobe, Japan

## 20592

20592^{2} = (7^{2} - 1)(10^{2} - 1)(12^{2} - 1)(25^{2} - 1).

by Yoshio Mimura, Kobe, Japan

## 20602

20602^{2} = 424442404 is a square consisting of 3 kind of even digits.

20602^{2} = 424442404 is a square pegged by 4.

by Yoshio Mimura, Kobe, Japan

## 20608

20608^{2} = (1^{2} + 7)(4^{2} + 7)(7^{2} + 7)(203^{2} + 7)

= (4^{2} + 7)(21^{2} + 7)(203^{2} + 7) = (4^{2} + 7)(7^{2} + 7)(21^{2} + 7)(27^{2} + 7).

by Yoshio Mimura, Kobe, Japan

## 20632

20632^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20670

20670^{2} = (2^{2} + 9)(9^{2} + 9)(16^{2} + 9)(37^{2} + 9).

by Yoshio Mimura, Kobe, Japan

## 20678

20678^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20691

20691^{2} = (1^{2} + 8)(5^{2} + 8)(7^{2} + 8)(159^{2} + 8) = (3^{2} + 2)(13^{2} + 2)(19^{2} + 2)(25^{2} + 2)

= (3^{2} + 2)(5^{2} + 2)(19^{2} + 2)(63^{2} + 2) = (7^{2} + 8)(17^{2} + 8)(159^{2} + 8).

by Yoshio Mimura, Kobe, Japan

## 20712

20712^{2}± 5 are primes.

by Yoshio Mimura, Kobe, Japan

## 20718

20718^{2} = 6^{3} + 9^{3} + 12^{3} + 83^{3} + 754^{3}.

by Yoshio Mimura, Kobe, Japan

## 20724

20724^{2} = S2(851) + S2(875), where S2(n) = 1^{2} + 2^{2} + ... + n^{2}.

by Yoshio Mimura, Kobe, Japan

## 20736

20736^{2}± 5 are primes.

20736 = 144^{2} is a zigzag square consisting of different digits.

by Yoshio Mimura, Kobe, Japan

## 20744

20744^{2} = 430313536 is a square pegged by 3.

by Yoshio Mimura, Kobe, Japan

## 20748

20748^{2} = (1^{2} + 3)(3^{2} + 3)(4^{2} + 3)(6^{2} + 3)(110^{2} + 3) = (1^{2} + 3)(4^{2} + 3)(33^{2} + 3)(72^{2} + 3)

= (1^{2} + 3)(4^{2} + 3)(5^{2} + 3)(6^{2} + 3)(72^{2} + 3) = (1^{2} + 3)(6^{2} + 3)(12^{2} + 3)(137^{2} + 3)

= (1^{2} + 3)(6^{2} + 3)(15^{2} + 3)(110^{2} + 3) = (1^{2} + 3)(6^{2} + 3)(23^{2} + 3)(72^{2} + 3)

= (15^{2} + 3)(19^{2} + 3)(72^{2} + 3) = (2^{2} + 3)(3^{2} + 3)(4^{2} + 3)(7^{2} + 3)(72^{2} + 3)

= (2^{2} + 3)(4^{2} + 3)(6^{2} + 3)(15^{2} + 3)(19^{2} + 3) = (2^{2} + 3)(6^{2} + 3)(9^{2} + 3)(137^{2} + 3)

= (2^{2} + 3)(7^{2} + 3)(15^{2} + 3)(72^{2} + 3) = (3^{2} + 3)(4^{2} + 3)(19^{2} + 3)(72^{2} + 3)

= (4^{2} + 3)(6^{2} + 3)(23^{2} + 3)(33^{2} + 3) = (4^{2} + 3)(7^{2} + 3)(9^{2} + 3)(72^{2} + 3).

by Yoshio Mimura, Kobe, Japan

## 20754

20754^{2} = 430728516 is a square consisting of different digits.

by Yoshio Mimura, Kobe, Japan

## 20758

20758^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20771

20771^{2} = 431434441 is a square consisting of 3 kinds of digits.

by Yoshio Mimura, Kobe, Japan

## 20798

20798^{2}± 3 are primes.

by Yoshio Mimura, Kobe, Japan

## 20800

20800^{2} = (1^{2} + 4)(2^{2} + 4)(3^{2} + 4)(6^{2} + 4)(10^{2} + 4)(14^{2} + 4) = (2^{2} + 4)(6^{2} + 4)(10^{2} + 4)(114^{2} + 4).

by Yoshio Mimura, Kobe, Japan

## 20826

20826^{2} = (13^{2} + 9)(15^{2} + 9)(102^{2} + 9) = (2^{2} + 9)(3^{2} + 9)(13^{2} + 9)(102^{2} + 9).

by Yoshio Mimura, Kobe, Japan

## 20832

20832^{2} = (1^{2} + 3)(3^{2} + 3)(5^{2} + 3)(11^{2} + 3)(51^{2} + 3).

by Yoshio Mimura, Kobe, Japan

## 20838

20838^{2} = 434222244 is a square consisting of 3 kinds of digits.

by Yoshio Mimura, Kobe, Japan

## 20898

20898^{2} = (1^{2} + 2)(2^{2} + 2)(5^{2} + 2)(16^{2} + 2)(59^{2} + 2) = (16^{2} + 2)(22^{2} + 2)(59^{2} + 2)

= (4^{2} + 2)(5^{2} + 2)(16^{2} + 2)(59^{2} + 2).

by Yoshio Mimura, Kobe, Japan

## 20904

20904^{2} = (1^{2} + 3)(3^{2} + 3)(6^{2} + 3)(8^{2} + 3)(59^{2} + 3).

by Yoshio Mimura, Kobe, Japan

## 20905

20905^{2} = (1^{2} + 4)(9349^{2} + 4).

by Yoshio Mimura, Kobe, Japan

## 20910

20910^{2} = (1^{2} + 9)(5^{2} + 9)(1134^{2} + 9).

by Yoshio Mimura, Kobe, Japan

## 20930

20930^{2} = 1026^{2} + 1027^{2} + 1028^{2} + ... + 1337^{2}.

by Yoshio Mimura, Kobe, Japan

## 20973

20973^{2}± 2 are primes.

by Yoshio Mimura, Kobe, Japan

## 20992

20992^{2} = 440664064 is a square consisting of 3 kinds of even digits.

by Yoshio Mimura, Kobe, Japan