What is the greatest common factor of 45 and 64?

The factors of 45 are 1, 3, 5, 9, 15, and 45

The factors of 64 are 1, 2, 4, 8, 16, 32, and 64.

The common factor is 1. Therefore, the greatest common factor is 1, which means the two numbers are relatively prime.
The Greatest Common Factor (GCF) is: 1