What are the common factors and greatest common factor of 3?

There is neither a greatest common factor nor common factors of a single number, such as 3, 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 3 are 1 and 3.

The prime factor of 3 is 3.

Examples:

The common factors of 3 and 20 are only 1; the greatest common factor is 1.

The common factors of 3 and 81 are 1 and 3; the greatest common factor is 3.