15 (number)

Fifteen redirects here. This article is relating to the number 15, pas au Rugby. For the year, to see 15.

15 (fifteen) is the Entier naturalness which follows 14 and which precedes 16.

In mathematics

Fifteen is a triangular Nombre, a hexagonal Nombre and the fourth Nombre of Beautiful. Fifteen is the double factorial of 5. Fifteen is a made up Nombre; its own dividers are 1, 3 and 5, it is a Nombre semi-first.

With only two exceptions, all the quadruplets of prime numbers frame a multiple of 15,15 itself being framed by the quadruplet (11, 13, 17, 19).

In hexadecimal, or very other bases higher, fifteen is represented by the letter F .

Fifteen is a magic Constante of a magic square of 3 by 3.

$\begin{bmatrix}
8 & 1 & 6 \ \
3 & 5 & 7 \ \
4 & 9 & 2 \ \
\end{bmatrix}$

In other fields

The Square of Lo Shu, used in the Feng shui, is a magic square of 3 by 3 whose magic Constante is 15.

15 years it is:

the age of a Quinceañera, a Spanish girl which celebrates its fifteenth birthday.
With the the United States, the age to obtain a driving license (or to pass it) in the jurisdictions where the age for a driving license is 16 years.

Fifteen is:

the telephone number of the SAMU
the Atomic number of the Phosphorus, a Non-metal.
the number of days in each 24 cycles of the Chinese Calendrier.
the number of players of a team of Rugby.

With the Rugby, the full back carries the n°15.

the number of pawns, that each side has at the beginning of a play of Backgammon.
a restaurant of London, opened by the famous chief Jamie Oliver.
the number of balls in the Eight ball, an alternative of the Billiards.
the number of years of Marriage of the weddings of Crystal.
historical Years: -15, 15, or 1915.
the n° of the French Department of the Cantal.
the number of the French highway A15 which starts from Villeneuve-the-Garenne to reach Cergy-Pontoise.

External bonds

Almanac and dictionary of the numbers (site of Gerard Villemin)
Wiktionnaire

Ru-sib: 15 (число)

Zh-yue: 15

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