GCF for 21 and 63
What is the Greatest Common Divisor of 21 and 63?
Answer
(Twenty-one)
Finding GCF for 21 and 63 using all factors (divisors) listing
The first method to find GCF for numbers 21 and 63 is to list all factors for both numbers and pick the highest common one:
All factors of 21: 1, 3, 7, 21
All factors of 63: 1, 3, 7, 9, 21, 63
So the Greatest Common Factor for 21 and 63 is 21
Finding GCF for 21 and 63 by Prime Factorization
The second method to find GCF for numbers 21 and 63 is to list all Prime Factors for both numbers and multiply the common ones:
All Prime Factors of 21: 3, 7
All Prime Factors of 63: 3, 3, 7
As we can see there are Prime Factors common to both numbers: 3, 7
Now we need to multiply them to find GCF: 3 × 7 = 21
Related Calculations
See Also
- Least Common Multiple - Find the Least Common Multiple (LCM) of two numbers
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GCF Table
About "Greatest Common Factor" Calculator
Greatest Common Factor (GCF) also known as the Greatest Common Divisor (GCD) or Highest Common Factor (HCF) - it is the largest positive integer that divides each of the integers with zero remainder.