# What is the GCF of 21 and 63?

##### 1 Answer

#### Explanation:

The GCF (greatest common factor) of two numbers is the greatest number which is a factor of both of them.

The factors of

The factors of

The greatest number which is on both lists is

The GCF (greatest common factor) of two numbers is the greatest number which is a factor of both of them.

The factors of

The factors of

The greatest number which is on both lists is