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Online Calculators > Math Calculators
GCF of 20 and 81
What is the GCF of 20 and 81? - The GCF of 20 and 81 is 1.
Follow the step by step instructions on how to find the great common factor of 20 and 81.
What is the greatest common factor of 20 and 81?
How to find the gcf of 20 and 81?
Method 1 - Listing Factors
To find the gcf of 20 and 81, we first need to find the factors of 20 and 81 and then choose the greatest common factor that are dividable by both 20 and 81.
Factors of 20 = 1, 2, 4, 5, 10, 20
Factors of 81 = 1, 3, 9, 27, 81
The greatest common factor of 20 and 81 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 20 and 81 is by using the prime factorization method.
To use prime factorization, we first need to find the prime factors of 20 and 81, and then get the GCF by multiplying all the common prime factors from the two sets.
Prime factorization of 20 = 2 x 2 x 5
Prime factorization of 81 = 3 x 3 x 3 x 3
Common prime factors = = 1
GCF of 19 and 81
GCF of 21 and 81
GCF of 20 and 82
GCF of 20 and 80
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