What is the Greatest Common Factor of 21985 and 21990?

Greatest common factor (GCF) of 21985 and 21990 is 5.

GCF(21985,21990) = 5

We will now calculate the prime factors of 21985 and 21990, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 21985 and 21990.

How to find the GCF of 21985 and 21990?

We will first find the prime factorization of 21985 and 21990. After we will calculate the factors of 21985 and 21990 and find the biggest common factor number .

Step-1: Prime Factorization of 21985

Prime factors of 21985 are 5, 4397. Prime factorization of 21985 in exponential form is:

21985 = 5¹ × 4397¹

Step-2: Prime Factorization of 21990

Prime factors of 21990 are 2, 3, 5, 733. Prime factorization of 21990 in exponential form is:

21990 = 2¹ × 3¹ × 5¹ × 733¹

Step-3: Factors of 21985

List of positive integer factors of 21985 that divides 21985 without a remainder.

1, 5, 4397

Step-4: Factors of 21990

List of positive integer factors of 21990 that divides 21985 without a remainder.

1, 2, 3, 5, 6, 10, 15, 30, 733, 1466, 2199, 3665, 4398, 7330, 10995

Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 21985 and 21990. The biggest common factor number is the GCF number.
So the greatest common factor 21985 and 21990 is 5.

Also check out the Least Common Multiple of 21985 and 21990