LCM for 7 and 21

The first method to find LCM for numbers 7 and 21 is to find Greatest Common Factor (GCF) of these numbers. Here's the formula:

LCM = (Number1 × Number2) ÷ GCF

GCF of numbers 7 and 21 is 7, so

LCM = (7 × 21) ÷ 7

LCM = 147 ÷ 7

LCM = 21

The second method to find LCM for numbers 7 and 21 is to list out the common multiples for both nubmers and pick the first which matching:

Multiples of 7: 7, 14, 21, 28, 35

Multiples of 21: 21, 42, 63, 84, 105, [...], 21

So the LCM for 7 and 21 is 21

Another method to find LCM for numbers 7 and 21 is to list all Prime Factors for both numbers and multiply the highest exponent prime factors: