GCF and LCM of 28 and 42
The greatest common factor and least common multiple of 28 and 42.
GCF of 28 and 42
14
LCM of 28 and 42
84
How it works
Break each number into its prime factors:
- 28 = 2² × 7
- 42 = 2 × 3 × 7
The GCF (14) multiplies the primes both share, at the lowest power each appears. The LCM (84) multiplies every prime that appears in either number, at the highest power — which is also 28 × 42 ÷ 14 = 84.
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Frequently asked questions
What is the GCF of 28 and 42?+
The greatest common factor (GCF) of 28 and 42 is 14 — the largest number that divides both 28 and 42 with no remainder.
What is the LCM of 28 and 42?+
The least common multiple (LCM) of 28 and 42 is 84 — the smallest number that both 28 and 42 divide into. It equals 28 × 42 ÷ GCF = 1176 ÷ 14 = 84.