18 (eighteen) is the natural number following 17 and preceding 19.
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Cardinal | eighteen | |||
Ordinal | 18th (eighteenth) | |||
Numeral system | octodecimal | |||
Factorization | 2 × 32 | |||
Divisors | 1, 2, 3, 6, 9, 18 | |||
Greek numeral | ΙΗ´ | |||
Roman numeral | XVIII | |||
Binary | 100102 | |||
Ternary | 2003 | |||
Senary | 306 | |||
Octal | 228 | |||
Duodecimal | 1612 | |||
Hexadecimal | 1216 | |||
Hebrew numeral | י"ח | |||
Babylonian numeral | 𒌋𒐜 |
In most countries, 18 is the age of majority, in which a minor becomes a legal adult. It is also the voting age, marriageable age, drinking age and smoking age in most countries, though sometimes these ages are different than the age of majority. Many websites restrict adult content to visitors who claim to be aged over 18.