A factor is a divisor - a number that will evenly divide into another number. The greatest common factor of two or more numbers is the largest factor that both numbers have in common. One way to determine the common factors and greatest common factor is to find all the factors of the numbers and compare them. The factors of 19 are 1 and 19. The factors of 21 are 1, 3, 7, and 21. The only common factor is 1. Therefore, the greatest common factor is 1, which means the numbers are relatively prime.
The greatest common factor of 21 and 39 is 3
The greatest common factor of 21 and 77 is 7.
The greatest factor of 21 and 16 is 21, which is a factor of 21 but not of 16.
The greatest common factor of 21 and 175 is 7.
The greatest common factor of 21 and 75 is 3.
The Greatest Common Factor of 21, 9 is 3.
The greatest common factor of 21 and 322 is 7.
The greatest common factor of 21 and 162 is 3.
The greatest common factor of 21 and 102 is 3.
The greatest common factor of 21 and 56 is 7.
The Greatest Common Factor of 14 and 21 is 7.