Greatest Common Factor of 517 and 524 = 1 Step 1: Find the prime factorization of 517 517 = 11 x 47 Step 2: Find the prime factorization of 524 524 = 2 x 2 x 131 Step 3: Multiply those factors both numbers have in common in steps i) or ii) above to find the gcf: GCF = = 1 Step 4: Therefore, the greatest common factor of 517 and 524 is 1.