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18 in words

18

eighteen

18 is written eighteen.

Ways to write it

As an ordinal: eighteenth
Roman numeral: XVIII
Expanded form: 10 + 8

Place value

Place	Digit	Value
tens	1	10
ones	8	8

Number facts

Even or odd: Even
Prime or composite: Composite
Factors: 1, 2, 3, 6, 9 and 18 (6 factors)
First 10 multiples: 18, 36, 54, 72, 90, 108, 126, 144, 162, 180
Square: 18 × 18 = 324
Square root: ≈ 4.24
Sum of the digits: 1 + 8 = 9
Rounded to the nearest 10: 20
Number before: 17
Number after: 19
In binary: 10010

Quick check

What number comes just after 18?
Show the answer
19
Is 18 even or odd?
Show the answer
Even
What is 18 + 10?
Show the answer
28

Practise with a game

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Place Value Quest

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Times Tables Challenge

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Frequently asked questions

How do you write 18 in words?

18 is written "eighteen".

Is 18 a prime number?

No. 18 is a composite number, because it has more than two factors.

What are the factors of 18?

The factors of 18 are 1, 2, 3, 6, 9 and 18.

How do you write 18 in Roman numerals?

18 in Roman numerals is XVIII.