The greatest
factor that two numbers share.
Example 1:
What is the greatest common factor of 18 and 27?
The factors of 18 are 1, 18, 2, 9, 3, 6.
The factors of 27 are 1, 27, 3, 9.
The greatest factor that 18 and 27 share is 9. The greatest common factor (GCF) is 9.