What are the common factors of 4 and 10?

The factors of 4 are 1, 2, and 4.

The factors of 10 are 1, 2, 5, and 10.

The common factors of 4 and 10 are 1 and 2. This means 2 is the greatest common factor (GCF), and 2 is the only significant common factor, since all numbers have 1 as a factor.