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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.

