LCM for 20 and 21

"Least Common Multiple" Calculator

Least Common Multiple of

and

What's the Least Common Multiple (LCM) of 20 and 21?

Answer

LCM of 20 and 21 is 420

(Four hundred twenty)

Finding LCM for 20 and 21 using GCF 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 numbers and pick the first one that matches:

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

Related Calculations

See Also

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 20 and 21? (The answer is: 420). Select the first number (e.g. '20') and the second number (e.g. '21'). 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
521105
62142
72121
821168
92163
1021210
1121231
122184
1321273
142142
1521105
1621336
1721357
1821126
1921399
2021420
212121
2221462
2321483
2421168
2521525
2621546
2721189
282184
2921609
3021210
3121651
3221672
3321231
3421714

FAQ

What's the Least Common Multiple (LCM) of 20 and 21?

LCM of 20 and 21 is 420

How to find the LCM of 20 and 21 using prime factorization?

To find the LCM of 20 and 21, find all prime factors of both numbers, then multiply the highest power of each prime factor. The result is 420.

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 20 and 21: LCM = 420, GCF = 1.

See Also