GCF and LCM of 18 and 20
The greatest common factor and least common multiple of 18 and 20.
GCF of 18 and 20
2
LCM of 18 and 20
180
How it works
Break each number into its prime factors:
- 18 = 2 × 3²
- 20 = 2² × 5
The GCF (2) multiplies the primes both share, at the lowest power each appears. The LCM (180) multiplies every prime that appears in either number, at the highest power — which is also 18 × 20 ÷ 2 = 180.
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Frequently asked questions
What is the GCF of 18 and 20?+
The greatest common factor (GCF) of 18 and 20 is 2 — the largest number that divides both 18 and 20 with no remainder.
What is the LCM of 18 and 20?+
The least common multiple (LCM) of 18 and 20 is 180 — the smallest number that both 18 and 20 divide into. It equals 18 × 20 ÷ GCF = 360 ÷ 2 = 180.