A

David

Darling

ten

Ten is the base of our familiar number system, which stems directly from the fact that we have ten fingers on which to count. Ten is the only triangular number that is a sum of consecutive odd squares (10 = 12 + 32) and the only composite integer such that all of its positive integer divisors other than 1 are of the form x2 + 1 (2 = 12 + 1, 5 = 22 + 1, 10 = 32 + 1). Strange but true: the lifespan of a taste bud is ten days.