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