LCM for 21 and 28

"Least Common Multiple" Calculator

Least Common Multiple of

and

What's the Least Common Multiple (LCM) of 21 and 28?

Answer

LCM of 21 and 28 is 84

(Eighty-four)

Finding LCM for 21 and 28 using GCF of these numbers

The first method to find LCM for numbers 21 and 28 is to find Greatest Common Factor (GCF) of these numbers. Here's the formula:

LCM = (Number1 × Number2) ÷ GCF

GCF of numbers 21 and 28 is 7, so

LCM = (21 × 28) ÷ 7

LCM = 588 ÷ 7

LCM = 84

Finding LCM for 21 and 28 by Listing Multiples

The second method to find LCM for numbers 21 and 28 is to list out the common multiples for both numbers and pick the first one that matches:

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

Multiples of 28: 28, 56, 84, 112, 140

So the LCM for 21 and 28 is 84

Finding LCM for 21 and 28 by Prime Factorization

Another method to find LCM for numbers 21 and 28 is to list all Prime Factors for both numbers and multiply the highest exponent prime factors:

All Prime Factors of 21: 3, 7 (exponent form: 31, 71)

All Prime Factors of 28: 2, 2, 7 (exponent form: 22, 71)

31 × 71 × 22 = 84

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About "Least Common Multiple" Calculator

This calculator will help you find the Least Common Multiple (LCM) of two numbers. For example, it can help you find out what's the Least Common Multiple (LCM) of 21 and 28? (The answer is: 84). Select the first number (e.g. '21') and the second number (e.g. '28'). After that hit the 'Calculate' button.
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

"Least Common Multiple" Calculator

Least Common Multiple of

and

LCM Table

Number 1Number 2LCM
62884
72828
82856
928252
1028140
1128308
122884
1328364
142828
1528420
1628112
1728476
1828252
1928532
2028140
212884
2228308
2328644
2428168
2528700
2628364
2728756
282828
2928812
3028420
3128868
3228224
3328924
3428476
3528140

FAQ

What's the Least Common Multiple (LCM) of 21 and 28?

LCM of 21 and 28 is 84

How to find the LCM of 21 and 28 using prime factorization?

To find the LCM of 21 and 28, find all prime factors of both numbers, then multiply the highest power of each prime factor. The result is 84.

What is the difference between LCM and GCF?

LCM (Least Common Multiple) is the smallest number divisible by both numbers, while GCF (Greatest Common Factor) is the largest number that divides both. For 21 and 28: LCM = 84, GCF = 7.

See Also