Factors of 72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72
2, 4, 8, 12, 18, 24, 36, and 72 are multiples of its prime factor which is 2.
3, 6, 9, 18, 36, and 72 are multiples of its prime factor which is 3.
So there are all the factors that are multiples of its prime factor:
2, 3, 4, 6, 8, 9, 12, 18, 24, 36, and 72