What is the Greatest Common Factor of 21981 and 21987?

Greatest common factor (GCF) of 21981 and 21987 is 3.

GCF(21981,21987) = 3

We will now calculate the prime factors of 21981 and 21987, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 21981 and 21987.

How to find the GCF of 21981 and 21987?

We will first find the prime factorization of 21981 and 21987. After we will calculate the factors of 21981 and 21987 and find the biggest common factor number .

Step-1: Prime Factorization of 21981

Prime factors of 21981 are 3, 17, 431. Prime factorization of 21981 in exponential form is:

21981 = 3¹ × 17¹ × 431¹

Step-2: Prime Factorization of 21987

Prime factors of 21987 are 3, 7, 349. Prime factorization of 21987 in exponential form is:

21987 = 3² × 7¹ × 349¹

Step-3: Factors of 21981

List of positive integer factors of 21981 that divides 21981 without a remainder.

1, 3, 17, 51, 431, 1293, 7327

Step-4: Factors of 21987

List of positive integer factors of 21987 that divides 21981 without a remainder.

1, 3, 7, 9, 21, 63, 349, 1047, 2443, 3141, 7329

Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 21981 and 21987. The biggest common factor number is the GCF number.
So the greatest common factor 21981 and 21987 is 3.

Also check out the Least Common Multiple of 21981 and 21987