LCM for 4 and 21

The first method to find LCM for numbers 4 and 21 is to find Greatest Common Factor (GCF) of these numbers. Here's the formula:

LCM = (Number1 × Number2) ÷ GCF

GCF of numbers 4 and 21 is 1, so

LCM = (4 × 21) ÷ 1

LCM = 84 ÷ 1

LCM = 84

The second method to find LCM for numbers 4 and 21 is to list out the common multiples for both nubmers and pick the first which matching:

Multiples of 4: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, 80, 84, 88, 92

Multiples of 21: 21, 42, 63, 84, 105, 126

So the LCM for 4 and 21 is 84

Another method to find LCM for numbers 4 and 21 is to list all Prime Factors for both numbers and multiply the highest exponent prime factors: