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Online Calculators > Math Calculators
GCF of 21 and 40
What is the GCF of 21 and 40? - The GCF of 21 and 40 is 1.
Follow the step by step instructions on how to find the great common factor of 21 and 40.
What is the greatest common factor of 21 and 40?
How to find the gcf of 21 and 40?
Method 1 - Listing Factors
To find the gcf of 21 and 40, we first need to find the factors of 21 and 40 and then choose the greatest common factor that are dividable by both 21 and 40.
Factors of 21 = 1, 3, 7, 21
Factors of 40 = 1, 2, 4, 5, 8, 10, 20, 40
The greatest common factor of 21 and 40 is 1, because 1 is the largest number that is divisible by both numbers.
Method 2 - Prime Factorization
Another method to find the greatest common factor of 21 and 40 is by using the prime factorization method.
To use prime factorization, we first need to find the prime factors of 21 and 40, and then get the GCF by multiplying all the common prime factors from the two sets.
Prime factorization of 21 = 3 x 7
Prime factorization of 40 = 2 x 2 x 2 x 5
Common prime factors = = 1
GCF of 20 and 40
GCF of 22 and 40
GCF of 21 and 41
GCF of 21 and 39
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