Question: what is a common prime factor?
Answer: A common factor of two numbers is a factor that divides both numbers. The greatest common factor (GCF) of two numbers is the greatest number that divides both numbers. To find the GCF, take the prime factorization of both numbers. ... For example, the greatest common factor of 1,575 and 23,100 is 3×5×5×7 = 525.