LCM for 20 and 21
What's the Least Common Multiple (LCM) of 20 and 21?
(Four hundred twenty)
Finding LCM for 20 and 21 using GCF's of these numbers
The first method to find LCM for numbers 20 and 21 is to find Greatest Common Factor (GCF) of these numbers. Here's the formula:
LCM = (Number1 × Number2) ÷ GCF
GCF of numbers 20 and 21 is 1, so
LCM = (20 × 21) ÷ 1
LCM = 420 ÷ 1
LCM = 420
Finding LCM for 20 and 21 by Listing Multiples
The second method to find LCM for numbers 20 and 21 is to list out the common multiples for both nubmers and pick the first which matching:
Multiples of 20: 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 460
Multiples of 21: 21, 42, 63, 84, 105, 126, 147, 168, 189, 210, 231, 252, 273, 294, 315, 336, 357, 378, 399, 420, 441, 462
So the LCM for 20 and 21 is 420
Finding LCM for 20 and 21 by Prime Factorization
Another method to find LCM for numbers 20 and 21 is to list all Prime Factors for both numbers and multiply the highest exponent prime factors:
All Prime Factors of 20: 2, 2, 5 (exponent form: 22, 51)
All Prime Factors of 21: 3, 7 (exponent form: 31, 71)
22 × 51 × 31 × 71 = 420
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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