GCF for 21 and 84
"Greatest Common Factor" Calculator
What is the Greatest common Divisor of 21 and 84?
Answer: GCF of 21 and 84 is 21
(Twenty-one)
Finding GCF for 21 and 84 using all factors (divisors) listing
The first method to find GCF for numbers 21 and 84 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 84: 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84
So the Greatest Common Factor for 21 and 84 is 21
Finding GCF for 21 and 84 by Prime Factorization
The second method to find GCF for numbers 21 and 84 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 84: 2, 2, 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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About "Greatest Common Factor" Calculator
This calculator will help you find the greatest common factor (GCF) of two numbers. For example, it can help you find out what is the Greatest common Divisor of 21 and 84? (The answer is: 21). Select the first number (e.g. '21') and the second number (e.g. '84'). After that hit the 'Calculate' button.
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