what are the prime factors of 72
First, divide by 2: 72 = 2 x 36
Since 36 is even, divide again by 2: 72 = 2 x 2 x 18
Since 18 is even, divide agian by 2: 72 = 2 x 2 x 2 x 9
Since 9 = 3 x 3, finish: 72 = 2 x 2 x 2 x 3 x 3
So, the prime factors are 2 and 3; three 2s and two 3s.