Solutions by everydaycalculation.com

The GCF of 4 and 21 is 1.

- Find the prime factorization of 4

4 = 2 × 2 - Find the prime factorization of 21

21 = 3 × 7 - To find the GCF, multiply all the prime factors common to both numbers:

Therefore, GCF = 1

MathStep (Works offline)

Download our mobile app and learn how to find GCF of upto four numbers in your own time:

Android and iPhone/ iPad

Find hcf of: 8 & 42 12 & 63 20 & 105 28 & 147 8 & 21 4 & 42 12 & 21 4 & 63 20 & 21 4 & 105 28 & 21 4 & 147

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

The greatest common factor (GCF) is also known as greatest common divisor (GCD) or highest common factor (HCF).

© everydaycalculation.com