What are the common factors and greatest common factor of 20?

Answer 1

There is neither a greatest common factor nor common factors of a single number, such as 20, because there cannot be any form of common factor without two or more numbers to compare. Common factors are factors that the numbers being compared have in common. The greatest common factor is the largest factor that all the numbers being compared have in common. Thus, since there are not two or more numbers to compare, there are neither common factors nor a greatest common factor.

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

The prime factors of 20 are 2, 2, and 5.

Examples:

The common factors of 20 and 70 are 1, 2, 5, and 10; the greatest common factor is 10.

The common factors of 20 and 32 are 1, 2, and 4; the greatest common factor is 4.

The common factors of 20 and 140 are 1, 2, 4, 5, 10, and 20; the greatest common factor is 20.