GCF (HCF) of 42 and 63

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What is the Greatest Common Divisor of 42 and 63?

Answer

GCF (HCF) of 42 and 63 is
21

Common factors: 1, 3, 7, 21

21 divides both: 42 ÷ 21 = 2, 63 ÷ 21 = 3 — and 2 and 3 share no factor but 1, so no larger number divides both.

42 = 2 × 3 × 7

63 = 32 × 7

Prime4263Lowest power
22——
33323
7777

— = power 0: the prime is not a factor of this number, so it cannot be in the GCF.

GCF = 3 × 7 = 21

See Also

FAQ

What is the Greatest Common Divisor of 42 and 63?

GCF (HCF) of 42 and 63 is 21

How to find the GCF of 42 and 63?

You can find the GCF of 42 and 63 by listing all factors of both numbers and picking the greatest common one, or by prime factorization. The GCF of 42 and 63 is 21.

What prime factors do 42 and 63 share?

The prime factorizations of 42 and 63 have 3 × 7 in common, and multiplying those shared primes gives 21 — exactly the greatest common factor.

How does the GCF reduce the fraction 42/63?

Divide the numerator and the denominator by the GCF 21: 42 ÷ 21 = 2 and 63 ÷ 21 = 3. So 42/63 in lowest terms is 2/3.