LCM for 5, 15 and 20

"Least Common Multiple of 3 Numbers" Calculator
Least Common Multiple of
,
and

What's the Least Common Multiple (LCM) of 5, 15 and 20?

Answer

LCM of 5, 15 and 20 is
60

(Sixty)

60 is the smallest positive integer that 5, 15 and 20 all divide without a remainder — every other common multiple of the three is a multiple of it.

Finding the LCM of 5, 15 and 20 by Prime Factorization

Split all three numbers into prime factors, then take every prime that shows up in at least one of them, each raised to the highest power it reaches there. Multiplying those highest powers gives the least common multiple:

All Prime Factors of 5: 5 (exponent form: 5)

All Prime Factors of 15: 3 × 5 (exponent form: 3 × 5)

All Prime Factors of 20: 2 × 2 × 5 (exponent form: 22 × 5)

Prime factor51520Highest power
2——2222
3—3—3
55555

LCM = 22 × 3 × 5 = 60

Checking the LCM of 5, 15 and 20 Two Numbers at a Time

The least common multiple is associative, so three numbers can be handled as two pairs: first the LCM of the first two, then the LCM of that value and the third. Each pair goes through the two-number formula, which uses the greatest common divisor:

LCM(a, b) = (a × b) ÷ GCD(a, b)

LCM(5, 15) = (5 × 15) ÷ 5 = 75 ÷ 5 = 15

LCM(15, 20) = (15 × 20) ÷ 5 = 300 ÷ 5 = 60

LCM(5, 15, 20) = 60

The pairs may be taken in any order — 15 and 20 first, then 5 — and the answer is the same 60. That is exactly why the two routes on this page agree.

Related Calculations

See Also

About "Least Common Multiple of 3 Numbers" Calculator

This calculator finds the Least Common Multiple (LCM) of three numbers at once, without doing it in two passes. For example, it can help you find out what's the Least Common Multiple (LCM) of 5, 15 and 20? (The answer is: 60). Enter the first number (e.g. '5'), the second (e.g. '15') and the third (e.g. '20'), then hit the 'Calculate' button.
The Least Common Multiple of three numbers is the smallest positive integer that all three of them divide without a remainder
"Least Common Multiple of 3 Numbers" Calculator
Least Common Multiple of
,
and

LCM Table

Number 1Number 2Number 3LCM
551515
561530
5715105
5815120
591545
5101530
51115165
5121560
51315195
51415210
5151515
51516240
51517255
5151890
51519285
5152060
51521105
51522330
51523345
51524120
5152575
51526390
51527135
51528420
51529435
5153030
51531465
51532480
51533165
51534510

FAQ

What's the Least Common Multiple (LCM) of 5, 15 and 20?

LCM of 5, 15 and 20 is 60

How to find the LCM of 5, 15 and 20 by prime factorization?

Take every prime that appears in 5, 15 and 20 to the highest power it reaches in any one of them and multiply: 2² × 3 × 5 = 60.

Can you get the LCM of 5, 15 and 20 two numbers at a time?

Yes, and it is the check this page prints. The LCM of 5 and 15 is 15, and the LCM of 15 and 20 is 60 — the same answer, because the least common multiple is associative and does not depend on the order of the three numbers.

Is 60 divisible by 5, 15 and 20?

Yes, and by definition it is the smallest positive integer that is: 60 ÷ 5, 60 ÷ 15 and 60 ÷ 20 all come out whole. Any other common multiple of 5, 15 and 20 is a multiple of 60.

See Also