13 (number)
natural number
Thirteen is a number. It comes after twelve and before fourteen. It is an odd number.
| ||||
|---|---|---|---|---|
| Cardinal | thirteen | |||
| Ordinal | 13th (thirteenth) | |||
| Numeral system | tredecimal | |||
| Factorization | prime | |||
| Prime | 6th | |||
| Divisors | 1, 13 | |||
| Greek numeral | ΙΓ´ | |||
| Roman numeral | XIII | |||
| Binary | 11012 | |||
| Ternary | 1113 | |||
| Quaternary | 314 | |||
| Quinary | 235 | |||
| Senary | 216 | |||
| Octal | 158 | |||
| Duodecimal | 1112 | |||
| Hexadecimal | D16 | |||
| Vigesimal | D20 | |||
| Base 36 | D36 | |||
Many people think thirteen is an unlucky number, especially when Friday is the thirteenth day of the month. This is a superstition. There is no proof that thirteen is an unlucky number.
Floors in tall buildings often skip floor thirteen, or reserve it for a mechanical floor. The idea of thirteen as an unlucky number is from pagan Norse mythology. It was believed to be unlucky to have thirteen people sitting at a table at a meal, and death is number thirteen in the tarot deck.
In Roman numerals, 13 is written as XIII.
