Wednesday, February 9, 2011

687

687 = 3 x 229.

687 is a number that cannot be written as a sum of three squares.

687 is 2001 in base 7 and 575 in base 11. It is 22233 in base 4 and 223 in base 18.

687 primes less than 104 do not contain the digit 9.

In the Harry Potter books and movies, the Potter family vault number at Gringotts Bank is 687.

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