# 264 (number)

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 ← 259 260 261 →
Cardinal two hundred and sixty
Ordinal 260th
(two hundred and sixtieth)
Factorization 22· 5 · 13
Roman numeral CCLX
Binary 1000001002
Ternary 1001223
Quaternary 100104
Octal 4048
Duodecimal 19812
Vigesimal D020
Base 36 7836

260 (two hundred [and] sixty) is the magic constant of the n×n normal magic square and n-queens problem for n = 8, the size of an actual chess board.

260 is also the magic constant of the Franklin magic square devised by Benjamin Franklin.

 52 61 4 13 20 29 36 45 14 3 62 51 46 35 30 19 53 60 5 12 21 28 37 44 11 6 59 54 43 38 27 22 55 58 7 10 23 26 39 42 9 8 57 56 41 40 25 24 50 63 2 15 18 31 34 47 16 1 64 49 48 33 32 17

The minor diagonal gives 260, and in addition a number of combinations of two half diagonals of four numbers from a corner to the center give 260.

260 may also refer to the years AD 260 and 260 BC.

## 261–269

261 = 32·29, nonagonal number, Harshad number, number of possible unfolded tesseract patterns

262 = 2·131, meandric number, open meandric number, untouchable number

263 prime, safe prime, sum of five consecutive primes (43 + 47 + 53 + 59 + 61), balanced prime, Chen prime, Eisenstein prime with no imaginary part, strictly non-palindromic number

265 = 5·53, Padovan number, centered square number, Smith number, subfactorial 6.

266 = 2·7·19, sphenic number, Harshad number, nontotient, noncototient, self number, repdigit in base 11 (222). 266 is also the index of the largest proper subgroups of the sporadic group known as the Janko group J1.

267 = 3·89, the number of groups of order 64, see [1].

267: Area code for Pennsylvania, USA (Philadelphia area including its suburbs in eastern Montgomery County and most of Bucks County, overlays with 215)

268 = 22·67, noncototient, untouchable number

269 prime, twin prime with 271, sum of three consecutive primes (83 + 89 + 97), Chen prime, Eisenstein prime with no imaginary part, highly cototient number, strictly non-palindromic number