The greatest common factor (GCF) is the largest positive integer that divides two or more numbers without leaving a remainder. For example, for the numbers 12 and 18, the GCF is 6 because it is the largest number that both 12 and 18 are divisible by. The GCF can be found by listing the factors of each number and finding the largest number that appears in both lists, or by using prime factorization.
