Question: which is the greatest common factor of 18 27 and 45?
Answer: The prime factorization of 18 is 2 x 3 x 3 = 18. The prime factorization of 27 is 3 x 3 x 3 = 27. The occurrences of common prime factors of 18 and 27 are 3 and 3. So the greatest common factor of 18 and 27 is 3 x 3 = 9.