What is the greatest common factor of 15 36 and 70?

The GCF of 15, 36, and 70 is 1.

The prime factorization of 15 is 3*5
The prime factorization of 36 is 2*2*3*3
The prime factorization of 70 is 2*5*7

Since they have no common factors, they are coprime, and their GCF is 1.