GCF and LCM of 3 and 7
The greatest common factor and least common multiple of 3 and 7.
GCF of 3 and 7
1
LCM of 3 and 7
21
How it works
Break each number into its prime factors:
- 3 = 3
- 7 = 7
The GCF (1) multiplies the primes both share, at the lowest power each appears. The LCM (21) multiplies every prime that appears in either number, at the highest power — which is also 3 × 7 ÷ 1 = 21.
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Frequently asked questions
What is the GCF of 3 and 7?+
The greatest common factor (GCF) of 3 and 7 is 1 — the largest number that divides both 3 and 7 with no remainder.
What is the LCM of 3 and 7?+
The least common multiple (LCM) of 3 and 7 is 21 — the smallest number that both 3 and 7 divide into. It equals 3 × 7 ÷ GCF = 21 ÷ 1 = 21.