Solutions by everydaycalculation.com

The gcf of 21 and 91 is 7.

- Find the prime factorization of 21

21 = 3 × 7 - Find the prime factorization of 91

91 = 7 × 13 - To find the gcf, multiply all the prime factors common to both numbers:

Therefore, GCF = 7

The greatest common factor (gcf) is also known as greatest common divisor (gcd) or highest common factor (hcf).

Find hcf of: 42 & 182 63 & 273 105 & 455 147 & 637 3 & 13 42 & 91 21 & 182 63 & 91 21 & 273 105 & 91 21 & 455 147 & 91 21 & 637

Enter two numbers separate by comma. To find gcf of more than two numbers, click here.

© everydaycalculation.com