Question: what is the greatest common factor in 63 and 40?
Answer: The prime factorization of 40 is: 2 x 2 x 2 x 5. The prime factorization of 63 is: 3 x 3 x 7. The prime factors and multiplicities 40 and 63 have in common are: 1. 1 is the gcf of 40 and 63. gcf(40,63) = 1.