What is the Greatest Common Factor of 1815 and 1821?

Greatest common factor (GCF) of 1815 and 1821 is 3.

GCF(1815,1821) = 3

We will now calculate the prime factors of 1815 and 1821, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 1815 and 1821.

How to find the GCF of 1815 and 1821?

We will first find the prime factorization of 1815 and 1821. After we will calculate the factors of 1815 and 1821 and find the biggest common factor number .

Step-1: Prime Factorization of 1815

Prime factors of 1815 are 3, 5, 11. Prime factorization of 1815 in exponential form is:

1815 = 3¹ × 5¹ × 11²

Step-2: Prime Factorization of 1821

Prime factors of 1821 are 3, 607. Prime factorization of 1821 in exponential form is:

1821 = 3¹ × 607¹

Step-3: Factors of 1815

List of positive integer factors of 1815 that divides 1815 without a remainder.

1, 3, 5, 11, 15, 33, 55, 121, 165, 363, 605

Step-4: Factors of 1821

List of positive integer factors of 1821 that divides 1815 without a remainder.

1, 3, 607

Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 1815 and 1821. The biggest common factor number is the GCF number.
So the greatest common factor 1815 and 1821 is 3.

Also check out the Least Common Multiple of 1815 and 1821