**Prime factorization**

*Prime factorization* is finding the factors of a number that are
all prime. Here's how you do it:
Find 2 factors of your number.
Then look at your 2 factors and determine if one or both of
them is not prime. If it is not a prime factor it. Repeat this process
until all your factors are prime. Here's an example:

Find the prime factors of the number 84:
84
/ \
42 x 2 (84 is 42 times 2)
/ \
21 x 2 (42 is 21 times 2)
/ \
7 x 3 (21 is 7 times 3)
(7 and 3 are both prime, so we stop!)

So the prime factors of 84 are 7 x 3 x 2 x 2.

Now, here's a problem for you: Find the prime factors of 60.