No, the GFC is the greatest factor you can find in both numbers. For example, the GFC of 12 and 6 is 3. If you list the factors of both numbers, the factors of 12 is 2,3,4, and 6. The factors of 6 are 2 and 3. If you compare both of the number's factors, 3 is the greatest one that appears in both the numbers.