What is the Greatest Common Factor of 21840 and 21855?

Greatest common factor (GCF) of 21840 and 21855 is 15.

GCF(21840,21855) = 15

We will now calculate the prime factors of 21840 and 21855, than find the greatest common factor (greatest common divisor (gcd)) of the numbers by matching the biggest common factor of 21840 and 21855.

How to find the GCF of 21840 and 21855?

We will first find the prime factorization of 21840 and 21855. After we will calculate the factors of 21840 and 21855 and find the biggest common factor number .

Step-1: Prime Factorization of 21840

Prime factors of 21840 are 2, 3, 5, 7, 13. Prime factorization of 21840 in exponential form is:

21840 = 2⁴ × 3¹ × 5¹ × 7¹ × 13¹

Step-2: Prime Factorization of 21855

Prime factors of 21855 are 3, 5, 31, 47. Prime factorization of 21855 in exponential form is:

21855 = 3¹ × 5¹ × 31¹ × 47¹

Step-3: Factors of 21840

List of positive integer factors of 21840 that divides 21840 without a remainder.

1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 13, 14, 15, 16, 20, 21, 24, 26, 28, 30, 35, 39, 40, 42, 48, 52, 56, 60, 65, 70, 78, 80, 84, 91, 104, 105, 112, 120, 130, 140, 156, 168, 182, 195, 208, 210, 240, 260, 273, 280, 312, 336, 364, 390, 420, 455, 520, 546, 560, 624, 728, 780, 840, 910, 1040, 1092, 1365, 1456, 1560, 1680, 1820, 2184, 2730, 3120, 3640, 4368, 5460, 7280, 10920

Step-4: Factors of 21855

List of positive integer factors of 21855 that divides 21840 without a remainder.

1, 3, 5, 15, 31, 47, 93, 141, 155, 235, 465, 705, 1457, 4371, 7285

Final Step: Biggest Common Factor Number

We found the factors and prime factorization of 21840 and 21855. The biggest common factor number is the GCF number.
So the greatest common factor 21840 and 21855 is 15.

Also check out the Least Common Multiple of 21840 and 21855