18 (number)

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← 17 18 19 →
Cardinaleighteen
Ordinal18th
(eighteenth)
Factorization2 × 32
Greek numeralΙΗ´
Roman numeralXVIII
Binary100102
Ternary2003
Quaternary1024
Quinary335
Senary306
Octal228
Duodecimal1612
Hexadecimal1216
VigesimalI20
Base 36I36

18 (also written as eighteen or ten-eight) 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 2x3² in factored form.