13 (number)

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12 13 14
Cardinal thirteen
Ordinal 13th
(thirteenth)
Factorization prime
Prime 6th
Divisors 1, 13
Roman numeral XIII
Binary 11012
Ternary 1113
Quaternary 314
Quinary 235
Senary 216
Octal 158
Duodecimal 1112
Hexadecimal D16
Vigesimal D20
Base 36 D36

Thirteen is a number. It comes after twelve and before fourteen. It is an uneven number.

Many people think thirteen is an unlucky number, especially when it occurs on Friday 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. The idea of thirteen as an unlucky number was created in Norse mythology. It is supposed to be unlucky to have thirteen people sitting at a table at a meal. Death is number thirteen in the tarot deck.

In Roman numerals, 13 is written as XIII.