Solution: The GCF of 65 and 39 is 13MethodsHow to find the GCF of 65 and 39 using Prime FactorizationOne way to find the GCF of 65 and 39 is to compare the prime factorization of each number. To find the prime factorization, you can follow the instructions for each number here:What are the Factors of 65?What are the Factors of 39?Here is the prime factorization of 65:51×1315^1 × 13^151×131And this is the prime factorization of 39:31×1313^1 × 13^131×131When you compare the prime factorization of these two numbers, you can see that there are matching prime factors. You can now find the Greatest Common Factor of 65 and 39 by multiplying all the matching prime factors to get a GCF of 65 and 39 as 169:Thus, the GCF of 65 and 39 is: 169How to Find the GCF of 65 and 39 by Listing All Common FactorsThe first step to this method of finding the Greatest Common Factor of 65 and 39 is to find and list all the factors of each number. Again, you can see how this is done by looking at the “Factors of” articles that are linked to above.Let’s take a look at the factors for each of these numbers, 65 and 39:Factors of 65: 1, 5, 13, 65Factors of 39: 1, 3, 13, 39When you compare the two lists of factors, you can see that the common factor(s) are 1, 13. Since 13 is the largest of these common factors, the GCF of 65 and 39 would be 13.Find the GCF of Other Number PairsWant more practice? Try some of these other GCF problems:What is the GCF of 87 and 119?What is the GCF of 52 and 68?What is the GCF of 106 and 85?What is the GCF of 40 and 71?What is the GCF of 46 and 99?