LCM for 3 and 21
What's the Least Common Multiple (LCM) of 3 and 21?
(Twenty-one)
Finding LCM for 3 and 21 using GCF's of these numbers
The first method to find LCM for numbers 3 and 21 is to find Greatest Common Factor (GCF) of these numbers. Here's the formula:
LCM = (Number1 × Number2) ÷ GCF
GCF of numbers 3 and 21 is 3, so
LCM = (3 × 21) ÷ 3
LCM = 63 ÷ 3
LCM = 21
Finding LCM for 3 and 21 by Listing Multiples
The second method to find LCM for numbers 3 and 21 is to list out the common multiples for both nubmers and pick the first which matching:
Multiples of 3: 3, 6, 9, 12, 15, 18, 21, 24, 27
Multiples of 21: 21, 42, 63, 84, 105, 126, 147, 168, 189, [...], 21
So the LCM for 3 and 21 is 21
Finding LCM for 3 and 21 by Prime Factorization
Another method to find LCM for numbers 3 and 21 is to list all Prime Factors for both numbers and multiply the highest exponent prime factors:
All Prime Factors of 3: 3 (exponent form: 31)
All Prime Factors of 21: 3, 7 (exponent form: 31, 71)
31 × 71 = 21
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LCM Table
About "Least Common Multiple" Calculator
Least Common Multiple (LCM) also known as the Lowest Common Multiple or Smallest Common Multiple of 2 numbers - it is the smallest positive integer that is divisible by both numbers