What are the common factors of 16 and 20?

The common factors of 16 and 20 are: 1, 2, 4.

Factors of 20: 1, 2, 4, 5, 10, and 20

Factors of 16: 1, 2, 4, 8, and 16

The common factors of 20 and 16 are 1, 2, and 4, and the GCF of 20 and 16 is 4.