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.