>>114725270! the factorial has nothing to do with 0 the integer. The factorial operation is the product of all positive integers from 1 up to the specified number. So, 0! is simply the empty product of this operation, which must be equal to 1. A simple example is to obtain the correct result for "n choose k" with k=0 or k=n, i.e. from calculating n!/(k!*(n-k)!). There is exactly one way to choose 0 elements of a set of n objects, and exactly one way to choose all n of the objects.
