It can't. 36 isn't prime. The prime factorization of 72 is 2 x 2 x 2 x 3 x 3. Since 36 is a factor of 72, its prime factorization is contained there. 2 x 2 x 3 x 3 = 36

To find the prime factorization, start with any two factor pairs of a number and factor until all factors are prime. 2 x 36 = 72 2 x 2 x 18 2 x 2 x 2 x 9 2 x 2 x 2 x 3 x 3 is the prime factorization of 72.