# Greatest Common Factor of 21 and 28

Greatest common factor (GCF) of 21 and 28 is 7.

GCF(21,28) = 7

We will now calculate the prime factors of 21 and 28, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 21 and 28.

GCF Calculator and

## Prime Factorization of 21

Prime factors of 21 are 3, 7. Prime factorization of 21 in exponential form is:

21 = 31 × 71

## Prime Factorization of 28

Prime factors of 28 are 2, 7. Prime factorization of 28 in exponential form is:

28 = 22 × 71

### Factors of 21

List of positive integer factors of 21 that divides 21 without a remainder.

1, 3, 7

### Factors of 28

List of positive integer factors of 28 that divides 21 without a remainder.

1, 2, 4, 7, 14

### Greatest Common Factor

We found the factors and prime factorization of 21 and 28. The biggest common factor number is the GCF number.
So the greatest common factor 21 and 28 is 7.

Also check out the Least Common Multiple of 21 and 28

#### Related Greatest Common Factors of 28

big man 2020-04-18 22:11:59

love it but could you also do 3 numbers

Guest 2019-02-26 18:12:32

love it but could you also do 3 numbers

sabi 2018-10-02 16:19:56

love it but could you also do 3 numbers..?