GCF for 9, 18 and 27

"Greatest Common Factor of 3 Numbers" Calculator
Greatest Common Factor of
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What's the Greatest Common Factor (GCF) of 9, 18 and 27?

Answer

GCF of 9, 18 and 27 is
9

(Nine)

9 is the largest positive integer that divides 9, 18 and 27 without a remainder — every other common divisor of the three divides it too.

Finding the GCF of 9, 18 and 27 by Prime Factorization

Split all three numbers into prime factors, then keep every prime that appears in all three of them, each taken as many times as it appears in the poorest factorization. Multiplying what is left gives the greatest common factor:

All Prime Factors of 9: 3 × 3 (exponent form: 32)

All Prime Factors of 18: 2 × 3 × 3 (exponent form: 2 × 32)

All Prime Factors of 27: 3 × 3 × 3 (exponent form: 33)

Prime factor91827Lowest power
2—2——
332323332

GCF = 3 × 3 = 9

Checking the GCF of 9, 18 and 27 Two Numbers at a Time

The greatest common factor is associative, so three numbers can be handled as two pairs — and this is what makes the Euclidean algorithm usable here: run it on the first pair, then run it again on that result and the third number.

GCF(a, b, c) = GCF(GCF(a, b), c)

GCF(9, 18) = 9

GCF(9, 27) = 9

GCF(9, 18, 27) = 9

The answer checks out by division — all three quotients come out whole:

9 ÷ 9 = 1

18 ÷ 9 = 2

27 ÷ 9 = 3

1, 2 and 3 have no common factor left — that is what makes 9 the greatest one.

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See Also

About "Greatest Common Factor of 3 Numbers" Calculator

This calculator finds the Greatest Common Factor (GCF) of three numbers at once, without doing it in two passes. For example, it can help you find out what's the Greatest Common Factor (GCF) of 9, 18 and 27? (The answer is: 9). Enter the first number (e.g. '9'), the second (e.g. '18') and the third (e.g. '27'), then hit the 'Calculate' button.
The Greatest Common Factor of three numbers — also called the greatest common divisor (GCD) or highest common factor (HCF) — is the largest positive integer that divides all three of them with zero remainder
"Greatest Common Factor of 3 Numbers" Calculator
Greatest Common Factor of
,
and

GCF Table

Number 1Number 2Number 3GCF
912183
913181
914181
915183
916181
917181
918189
918191
918201
918213
918221
918231
918243
918251
918261
918279
918281
918291
918303
918311
918321
918333
918341
918351
918369
918371
918381
918393
918401
918411

FAQ

What's the Greatest Common Factor (GCF) of 9, 18 and 27?

GCF of 9, 18 and 27 is 9

What prime factors do 9, 18 and 27 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 9, 18 and 27 two numbers at a time?

Yes, and it is the check this page prints. The GCF of 9 and 18 is 9, and the GCF of 9 and 27 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 9 : 18 : 27?

Divide every term by the GCF 9: 9 ÷ 9 = 1, 18 ÷ 9 = 2 and 27 ÷ 9 = 3. So 9 : 18 : 27 in lowest terms is 1 : 2 : 3, and no whole number other than 1 divides all three of those.

See Also