Find the GCF of 21 and 55. Please show work Break 21 and 55 down to prime factors 21 = (3)(7) 55 = (5)(11) We don't see any common factors at all. However, 1 is ALWAYS a common factor of ANY two integers, and if there are no other factors in common, then the answer is GCF = 1 So the answer is GCF = 1 Edwin