GCF for 18, 45 and 63

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What's the Greatest Common Factor (GCF) of 18, 45 and 63?

Answer

GCF of 18, 45 and 63 is
9

Common factors: 1, 3, 9

9 divides all three: 18 ÷ 9 = 2, 45 ÷ 9 = 5, 63 ÷ 9 = 7 — and 2, 5 and 7 have no factor but 1 common to all of them, so no larger number divides all three.

18 = 2 × 32

45 = 32 × 5

63 = 32 × 7

Prime184563Lowest power
22———
332323232
5—5——
7——7—

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

GCF = 32 = 9

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GCF Table

1st2nd3rdGCF
1845483
1845491
1845501
1845513
1845521
1845531
1845549
1845551
1845561
1845573
1845581
1845591
1845603
1845611
1845621
1845639
1845641
1845651
1845663
1845671
1845681
1845693
1845701
1845711
1845729
1845731
1845741
1845753
1845761
1845771

FAQ

What's the Greatest Common Factor (GCF) of 18, 45 and 63?

GCF of 18, 45 and 63 is 9

What prime factors do 18, 45 and 63 share?

All three factorizations contain 3 × 3, and multiplying those shared primes gives 9 — exactly the greatest common factor.

Can you get the GCF of 18, 45 and 63 two numbers at a time?

Yes. The GCF of 18 and 45 is 9, and the GCF of 9 and 63 is 9 — the same answer, because the greatest common factor is associative and does not depend on the order of the three numbers.

How does the GCF simplify the ratio 18 : 45 : 63?

Divide every term by the GCF 9: 18 ÷ 9 = 2, 45 ÷ 9 = 5 and 63 ÷ 9 = 7. So 18 : 45 : 63 in lowest terms is 2 : 5 : 7, and no whole number other than 1 divides all three of those.

See Also