What are the common factors of 15?

There are no common factors of 15 because there cannot be common factors without two or more numbers to compare. Common factors are factors that the numbers being compared have in common.

The factors of 15 are 1, 3, 5, and 15.

Examples:

The common factors of 6 and 15 are 1 and 3.

The common factors of 15 and 90 are 1, 3, 5, and 15.
1,5,3, and 15.