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The GCF of 21 and 25 is 1

Definition: 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 the 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 21 are 1, 3, 7, and 21.

The factors of 25 are 1, 5, and 25.

The only common factor is 1. Therefore, the greatest common factor is 1, which means the numbers are relatively prime.

The greatest common factor of 21 and 25, is 1.

The factors of 21 are: 1, 3, 7, 21

The factors of 25 are: 1, 5, 25

The common factors are: 1
The GCF is 1.

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Q: What is the greatest common factor of 21 and 25?
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