COMMON FACTORS

When two (or more) numbers have the same factor, that factor is called a common factor.

Example

Find all the common factors of 12 and 18.

Factors of 12 are 1, 2, 3, 4, 6, 12.
Factors of 18 are 1, 2, 3, 6, 18.
The common factors of 12 and 18 are 1, 2, 3 and 6.