natural number From Wikipedia, the free encyclopedia

**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.

| ||||
---|---|---|---|---|

Cardinal | eighteen | |||

Ordinal | 18th (eighteenth) | |||

Factorization | 2 × 3^{2} | |||

Greek numeral | ΙΗ´ | |||

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} |

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 2x3² in factored form.

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