LCM for 4 and 21
What's the Least Common Multiple (LCM) of 4 and 21?
(Eighty-four)
Finding LCM for 4 and 21 using GCF's of these numbers
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
Finding LCM for 4 and 21 by Listing Multiples
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
Finding LCM for 4 and 21 by Prime Factorization
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:
All Prime Factors of 4: 2, 2 (exponent form: 22)
All Prime Factors of 21: 3, 7 (exponent form: 31, 71)
22 × 31 × 71 = 84
Related Calculations
See Also
- Greatest Common Factor - Find the Greatest Common Factor (GCF) of two numbers
<a href="https://calculat.io/en/number/least-common-multiple-lcm-of/4--21">What is the LCM of 4 and 21? - Calculatio</a>
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