Thirteen

Thirteen. It is the natural number following twelve and preceding fourteen. As the sixth prime number, and the second Wilson prime, it holds a unique position in number theory. Across human civilization, it has accrued profound significance, ranging from mathematical curiosity to deep-seated superstition.

In mathematics

Thirteen is a prime number, specifically a twin prime with eleven and a cousin prime with seventeen. It is one of only three known Wilson primes, alongside five and five hundred sixty-three. In geometry, there is no regular polygon with thirteen sides that can be constructed using a compass and straightedge, as thirteen is not a Fermat prime. The Fibonacci sequence contains the number thirteen, and it is the number of Archimedean solids. The projective plane of order three has thirteen points and thirteen lines, a fundamental concept in finite geometry.

In culture and religion

In Christianity, thirteen is most famously associated with the Last Supper, where Jesus dined with his Twelve Apostles. This connection contributes to its perception as an unlucky number in many Western cultures. Conversely, in Sikhism, the number holds positive value, as the first edition of the sacred Guru Granth Sahib was installed in the Golden Temple in 1604. In pre-Columbian Mesoamerica, the Maya civilization used a sacred calendar of 260 days, composed of twenty periods of thirteen days each. Modern cultural references include the Thirteen Colonies that formed the United States and the Apollo 13 space mission.

In science and technology

On the periodic table, aluminium has an atomic number of thirteen. In the International System of Units, the prefix for 10⁻¹³ is "atto-". The standard human adult skeleton typically has thirteen rib pairs during early developmental stages, though most fuse to form the twelve pairs seen in adulthood. In computing, IPv4 addresses in the range 13.0.0.0/8 are owned by Xerox. Furthermore, thirteen is the number of pitch classes in the chromatic scale of Western music, spanning an octave.

In sports and games

In rugby union, the number thirteen jersey is worn by the outside centre, a key defensive and attacking position. Major League Soccer began with thirteen teams in its inaugural 1996 season. The board game Backgammon uses a board with twenty-four points, and the standard opening move often involves moving a piece thirteen spaces. In many forms of poker, such as Texas hold 'em, a standard deck yields 13 ranks of cards. The FIA Formula One World Championship has seen several drivers, including Pastor Maldonado and Mick Schumacher, race with the number 13 on their cars.

In history and superstition

The fear of the number thirteen is known as triskaidekaphobia. This superstition often manifests in the omission of a thirteenth floor in many hotels and skyscrapers, particularly in North America and Europe. A notable historical group, the Knights Templar, were arrested en masse on Friday the 13th in October 1307 on orders from King Philip IV of France. The Apollo 13 mission, which suffered a critical in-flight failure, further cemented the number's association with misfortune in the public consciousness, despite the successful return of its crew, Jim Lovell, Jack Swigert, and Fred Haise.

Category:Integers