What is the greatest common factor of 21 and 63?

To find the greatest common factor (GCF) of two numbers, you can determine the largest number that divides both of them evenly. Here's how you can find the GCF of 21 and 63:

Step 1: List the factors of each number.

Factors of 21: 1, 3, 7, 21
Factors of 63: 1, 3, 7, 9, 21, 63
Step 2: Identify the common factors.
Both 21 and 63 share the following factors: 1, 3, 7, and 21.

Step 3: Determine the greatest common factor.
The greatest common factor among these shared factors is 21.

So, the greatest common factor of 21 and 63 is 21.