What is the GCF of 4 and 20?
GCF (Greatest Common Factor) of the numbers 4 and 20 is the largest possible number which divides 4 and 20 exactly without any remainder, that is, leaving the remainder 0
Answer: GCF of 4 and 20 is 4
Let us see how to find the GCF of 4 and 20
Explanation:
Let us find the GCF of 4 and 20 by two methods.

GCF of 4 and 20 by Prime Factoirzation
Let's list out the prime factorization of 4 and 20.
Prime factorization of 4 = 2 × 2
Prime factoirzation of 20 = 2 × 2 × 5
The common prime factors in both the prime factorizations are the repeated factors of 2, that are, 2 and 2
GCF of 4 and 20 will be the product of these common prime factors. So, GCF of 4 and 20 is 2 × 2 = 4

GCF of 4 and 20 by Listing the Common Factors
Factors of 4: 1, 2, 4
Factors of 20: 1, 2, 4, 5, 10, 20
There are three common factors of 4 and 20, that are, 1, 2 and 4
So, GCF of 4 and 20 is 4
You can find the GCF in any of the above methods but the solution will be the same.