Factors of a number 'x' are numbers that can divide 'x' without remainder, ie, remainder = 0. So, choosing only the numbers that meet this criteria from the list above, we find that the numbers which divide 15 (including 15) with no remainder are: 15, 5, 3, 1.

So, the factors of the number 15 are: 15, 5, 3, 1.

As 15 is a composite number, we can factorize it, ie, express it in prime Factors as follows.

By factorizing 15 we get: 15 = 3 * 5.

Ie, 15 can be expressed as a product of prime numbers (3 * 5).