LCM for 7 and 21

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What's the Least Common Multiple (LCM) of 7 and 21?

Answer

LCM of 7 and 21 is
21

First common multiples: 21, 42, 63, …

As a common denominator: multiply the top and bottom of x/7 by 3.

7 divides 21 (21 ÷ 7 = 3), so the LCM is the larger number itself.

7 — prime

21 = 3 × 7

Prime721Highest power
3—33
7777

— = power 0: the prime is not a factor of this number; the LCM takes it from the number that has it.

LCM = 3 × 7 = 21

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LCM Table

Number 1Number 2LCM
7428
7535
7856
7963
71070
71177
71284
71391
71414
715105
716112
717119
718126
719133
720140
72121
722154
724168
725175
726182
727189
72828
730210
731217
734238
73535
739273
741287
743301
744308

FAQ

What's the Least Common Multiple (LCM) of 7 and 21?

LCM of 7 and 21 is 21

How to find the LCM of 7 and 21 using prime factorization?

To find the LCM of 7 and 21, find all prime factors of both numbers, then multiply the highest power of each prime factor. The result is 21.

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 7 and 21: LCM = 21, GCF = 7.

See Also