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# 18 (number)

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Cardinal | eighteen | |||

Ordinal |
18th (eighteenth) | |||

Factorization |
2 · 3^{2} | |||

Roman numeral | XVIII | |||

Binary |
10010_{2} | |||

Ternary |
200_{3} | |||

Quaternary |
102_{4} | |||

Quinary |
33_{5} | |||

Senary |
30_{6} | |||

Octal |
22_{8} | |||

Duodecimal |
16_{12} | |||

Hexadecimal |
12_{16} | |||

Vigesimal |
I_{20} | |||

Base 36 |
I_{36} |

This article is about the number eighteen. For the year, see 18.

**Eighteen** is a number. It comes between seventeen and nineteen, and is an even number. It is divisible by 1, 2, 3, 6, 9 and 18.
In most countries it is the age of majority, age of consent, and voting age.

In Roman numerals, 18 is written as **XVIII**.

The number 18 has many multiples such as: 36, 54, 72, 90, 108, and so on. The prime factorization of 18 is 3x3x2 in expanded form, and 3^2x2 in factored form.