What is the Least Common Multiple of 21405 and 21420?

Least common multiple or lowest common denominator (lcd) can be calculated in two way; with the LCM formula calculation of greatest common factor (GCF), or multiplying the prime factors with the highest exponent factor.

Least Common Multiple of 21405 and 21420 with GCF Formula

The formula of LCM is LCM(a,b) = ( a × b) / GCF(a,b).
We need to calculate greatest common factor 21405 and 21420, than apply into the LCM equation.

GCF(21405,21420) = 15
LCM(21405,21420) = ( 21405 × 21420) / 15
LCM(21405,21420) = 458495100 / 15
LCM(21405,21420) = 30566340

Least Common Multiple (LCM) of 21405 and 21420 with Primes

Least common multiple can be found by multiplying the highest exponent prime factors of 21405 and 21420. First we will calculate the prime factors of 21405 and 21420.

Prime Factorization of 21405

Prime Factorization of 21420

Now multiplying the highest exponent prime factors to calculate the LCM of 21405 and 21420.

LCM(21405,21420) = 3² × 5¹ × 1427¹ × 2² × 7¹ × 17¹
LCM(21405,21420) = 30566340