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23 (twenty-three) is the natural number following 22 and preceding 24.

In mathematics [link]

Twenty-three is the ninth prime number, the smallest odd prime that is not a twin prime. Twenty-three is also the fifth factorial prime, the third Woodall prime. It is an Eisenstein prime with no imaginary part and real part of the form 3n − 1.

Twenty-three is the sum of three other, consecutive, prime numbers; 5, 7 and 11. It is the first prime number showing this characteristic.

The fifth Sophie Germain prime and the fourth safe prime, 23 is the next to last member of the first Cunningham chain of the first kind to have five terms (2, 5, 11, 23, 47). Since 14! + 1 is a multiple of 23 but 23 is not one more than a multiple 14, 23 is a Pillai prime. 23 is the smallest odd prime to be a highly cototient number, as the solution to x − φ(x) for the integers 95, 119, 143, 529.

Twenty-three is the aliquot sum of two integers; the discrete semiprimes 57 and 85 and is the base of the 23-aliquot tree.

23 is the first prime P for which unique factorization of cyclotomic integers based on the Pth root of unity breaks down.

The sum of the first 23 primes is 874, which is divisible by 23, a property shared by few other numbers.^[1][2]

In the list of fortunate numbers, 23 occurs twice, since adding 23 to either the fifth or eighth primorial gives a prime number (namely 2333 and 9699713).

23 also has the distinction of being one of two integers that cannot be expressed as the sum of fewer than 9 cubes of integers (the other is 239). See Waring's problem.

23 is a Wedderburn–Etherington number. The codewords in the perfect (non-extended) binary Golay code are of size 23.

According to the birthday paradox, in a group of 23 (or more) randomly chosen people, the probability is more than 50% that some pair of them will have the same birthday.

There were 23 problems on David Hilbert's famous list of unsolved mathematical problems, presented to the International Congress of Mathematicians in Paris in 1900.

In base 10, 23 is the second Smarandache–Wellin prime, as it is the concatenation of the base 10 representations of the first two primes (2 and 3) and is itself also prime. It is also a happy number in base 10. 23! is 23 digits long in base 10. There are only three other numbers that have this property: 1, 22, and 24.

The natural logarithms of all positive integers lower than 23 are known to have binary BBP-type formulae.^[3]

In science [link]

• The atomic number of vanadium.
• The atomic mass number of the stable isotope of sodium.
• Normal human sex cells have 23 chromosomes.^[4] Other human cells have 46 chromosomes, arranged in 23 pairs.^[5]
• Scientific notation for the avogadro constant is written as 6.02214179(30)×10²³ mol^-1.^[6]
• Nobel Prize-winning economist John Forbes Nash, the inspiration for the film A Beautiful Mind, was obsessed with the number 23 and it featured prominently in his nervous breakdown. He claimed that Pope John XXIII was in fact himself, the evidence being that 23 was his favourite number. Nash also published only 23 scientific articles.
• 23 is the width of the Arecibo message, sent to space in search for extraterrestrial intelligence.

In technology [link]

23 is the TCP/IP port used for telnet and is the default for the telnet command.

In religion [link]

• Psalm 23, also known as the Shepherd Psalm, is possibly the most quoted and best known Psalm.^[7] Psalms is also the 23rd book in the Douay–Rheims Bible.
• In Islam, the Qur'an was revealed in a total of 23 years to Muhammad.^[8][9]
• Muslims believe the first verses of the Qur'an were revealed to the Islamic prophet Muhammad, on the 23rd night of the 9th Islamic month.^[10]
• In Abhidharma, the number of anomalous generic types (of a possible 72) - e.g., events are considered sui generis because they are not reducible to either mind or matter — is 23.
• Principia Discordia, the sacred text of Discordianism, holds that 23 (along with the discordian prime 5) is one of the sacred numbers of Eris, goddess of discord.
• The Ancient Chinese believed that numbers conveyed sexuality with even numbers representing femininity and odd representing masculinity. Prime numbers were considered the most masculine and special status was conferred on 23 as it contained not only two consecutive prime numbers (2 and 3) but also the only even prime number.

In popular culture [link]

Sports [link]

Michael Jordan, a star basketball player for the NBA, wore the number 23 on his jersey

The number 23 has been worn by and sometimes retired for a number of few prominent athletes. Michael Jordan wore number 23 when he played professional basketball with the Chicago Bulls and, later, the Washington Wizards -- except immediately following his comeback from baseball, when he wore number 45, and for one game in the 1990-91 season against the Orlando Magic when his jersey was stolen and he wore the number 12. Australian cricketer Shane Warne wore the number 23 during his career; Don Mattingly of the New York Yankees wore number 23; the New York Yankees retired the number in 1997. Ryne Sandberg, of the Chicago Cubs, wore number 23, which was retired on August 28, 2005. Bob Nystrom of the New York Islanders wore number 23 and has had the number retired in his honour. Bob Gainey, ex-General Manager and former player for the Montreal Canadiens, had his number 23 retired February 23, 2008. Australian Football Player Lance Franklin from the Hawthorn Hawks wears the number 23. The all star NHL player Alexander Edler also wore number 23

Manchester City F.C. retired their number 23 shirt in 2003 following the death of Marc-Vivien Foé who had held this squad number at the club. Foé collapsed and died while playing for Cameroon on June 26, 2003. Belgian team Brugge did the same when their number 23, François Sterchele, died in a car accident on May 8, 2008.

Upon signing for Real Madrid from Manchester United in 2003 David Beckham found the number 7 shirt that he had always worn at Manchester and while on England duty occupied by Madrid hero Raúl. He declined the offer of the number 4 shirt recently vacated by departing captain Fernando Hierro and instead picked the number 23 in reference to Michael Jordan.^[11][12] When he then moved to MLS team Los Angeles Galaxy in 2007, he again chose to wear the number 23 jersey. Later, when he was on loan at AC Milan during the American off-season, he wore the reversed number 32 instead as the number 23 was already in use at the club.

In Darts, 23 is "the lowest score you cannot get with a single Dart".

Music [link]

• Alfred Harth uses the number 23 in his artist name Alfred 23 Harth, or A23H, since the year 1+9+8+5 = 23.
• Several songs and albums use the number 23 as their titles, including Tristan Prettyman's debut album, the eleventh song from Tool's fourth full-length studio album 10,000 Days, "Viginti Tres" (Latin for twenty-three).
• Blonde Redhead have the album '23' and the song with the same name.
• Jimmy Eat World's song "23" appeared on their album Futures. The number also appears in the songs "Christmas Card" and "12."23".95" as well as on some items of clothing produced by the band.
• Four tet and Yellowcard both have songs titled "Twenty-Three".
• The Posies have a record called Dear 23
• The Church's 2009 studio album is called "Untitled 23"
• Spiral Tribe From its inception, the group was obsessed by the number 23. Members sometimes recorded under the moniker of SP23, and the record label itself was called Network 23.
• Carbon Based Lifeforms released a 2011 album titled "Twentythree."
• Noah23 has several albums which reference the number 23.
• Luna's song "23 Minutes in Brussels" (featuring Tom Verlaine) appears on their album "Penthouse."

Film and television [link]

• 23 is the jersey number of Nathan Royal Scott - a character on the WB/CW television series One Tree Hill]
• 23 is a German film about Karl Koch
• The Number 23 is a 2007 film starring Jim Carrey.
• 23 is one of The Numbers - 4, 8, 15, 16, 23, and 42 - featured in Lost.
• In The Matrix Reloaded, the Architect tells Neo it is of utmost importance to choose 23 people to repopulate Zion.
• In Jeepers Creepers, the Creeper appears every 23 years for 23 days to feast on human flesh.
• In the film Vantage Point, all flashbacks take place 23 minutes before the assassination attempt on the president.
• As revealed in Japanese film L: Change the World, 23 is the maximum number of days a person may live before he dies by the cause of writing his name in Death Note. Main protagonist L of the film L: Change the World, signs his name in Death Note so to die after 23 days.
• In the Monty Python film Life Of Brian there are 23 crosses on Calvary.
• In The Big Lebowski, the main characters deliberately use only lane 23 at the bowling alley.
• In Star Wars Episode IV: A New Hope, Luke Skywalker, Han Solo and Chewbacca sneak into detention block AA23 to rescue Princess Leia. The rescue attempt is botched and Leia escapes only by dodging Stormtroopers' laserfire. A police robot called 23 is included in Star Wars director George Lucas' first film, THX 1138.

Other fields [link]

• The 23 Enigma plays a prominent role in the plot of the Illuminatus! Trilogy by Robert Shea and Robert Anton Wilson.
• The 23, in South Africa, refers to the 23 conscientious objectors who publicly refused to do military service in the Apartheid army in 1987. The following years the number increased to 143 (in 1988) and 771 (in 1989), with Apartheid being dismantled from 1990 onwards.^[13]
• Julius Caesar was stabbed 23 times.^[14]
• In The Legend of Zelda: Ocarina of Time, within the first dungeon, a deku scrub states "The order is...2 3 1. Twenty-three is number one!" as a hint to defeating his brethren deeper in the dungeon.
• X-23 is a character in the Marvel Universe. She is named for being the 23rd attempt to create a female genetic twin of Wolverine after attempts to create a male clone failed.

References [link]

External links [link]

Wikimedia Commons has media related to: 23 (number)

• Article in the British newspaper The Mirror regarding the power of the number 23
• A Portal for 23 Knowledge and Culture
• 23 facts, 23 images, 23 gallery, and links to other 23's