What is the greatest common factor of 40 and 65?

A factor is a divisor - a number that will evenly divide into another number. The greatest common factor of two or more numbers is the largest factor that both numbers have in common.

One way to determine the common factors and greatest common factor is to find all the factors of the numbers and compare them.

The factors of 40 are 1, 2, 4, 5, 8, 10, 20, and 40.

The factors of 65 are 1, 5, 13, and 65.

The common factors are 1 and 5. Therefore, the greatest common factor is 5.