260 (number)

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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.

Cardinal Two hundred [and] sixty
Ordinal 260th
Factorization 260 = 2^2 \cdot 5 \cdot 13
Roman numeral CCLX
Binary 100000100
Hexadecimal 104

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.

[edit] Other numbers from 261 to 269

Two hundred [and] sixty-one 261 = 32·29, nonagonal number, Harshad number

Two hundred [and] sixty-one 261 is the number of possible unfolded tesseract patterns

Two hundred [and] sixty-two 262 = 2·131, meandric number, open meandric number, untouchable number

Two hundred [and] sixty-three 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

Two hundred [and] sixty-four 264 = 23·3·11, Harshad number

Two hundred [and] sixty-five 265 = 5·53, Padovan number, centered square number, Smith number, subfactorial 6. It's the 666th decimal of Pi in base 666, making it a hyper-evil number.

Two hundred [and] sixty-six 266 = 2·7·19, sphenic number, Harshad number, nontotient, noncototient, self number, repdigit in base 11 (222).

Two hundred [and] sixty-seven 267 = 3·89, the number of groups of order 64, see [1].

Two hundred [and] sixty-eight 268 = 22·67, noncototient, untouchable number

Two hundred [and] sixty-nine 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