# 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 = 1^{2} + 3^{2}) and the only composite integer such that all of its positive
integer divisors other than 1 are of the form *x*^{2} + 1 (2
= 1^{2} + 1, 5 = 2^{2} + 1, 10 = 3^{2} + 1). Strange
but true: the lifespan of a taste bud is ten days.