Find the prime factorization of the number 15?

Answer 1

15 ends with the number 5, and so therefore must be divisible by the number 5. Indeed, 15/5 = 3, so our first two factors of 15 are 5 and 3. Well, both 5 and 3 are prime numbers, so we're done. You would usually write this as 3 X 5.