Solutions by » GCF of two numbers

What is the GCF of 21 and 402?

The GCF of 21 and 402 is 3.

Steps to find GCF

  1. Find the prime factorization of 21
    21 = 3 × 7
  2. Find the prime factorization of 402
    402 = 2 × 3 × 67
  3. To find the GCF, multiply all the prime factors common to both numbers:

    Therefore, GCF = 3

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