18 (number)

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17 18 19
Cardinal eighteen
Ordinal 18th
(eighteenth)
Factorization 2 · 32
Roman numeral XVIII
Binary 100102
Ternary 2003
Quaternary 1024
Quinary 335
Senary 306
Octal 228
Duodecimal 1612
Hexadecimal 1216
Vigesimal I20
Base 36 I36

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.