19 (number)

19 (nineteen) is the natural number following 18 and preceding 20. It is a prime number.

← 18 19 20 →
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Cardinal	nineteen
Ordinal	19th (nineteenth)
Numeral system	nonadecimal
Factorization	prime
Prime	8th
Divisors	1, 19
Greek numeral	ΙΘ´
Roman numeral	XIX
Binary	100112
Ternary	2013
Octal	238
Duodecimal	1712
Hexadecimal	1316

Mathematics

19 is a centered triangular number

19 is the 8th prime number, the seventh Mersenne prime exponent,[1] and the second base-10 repunit prime exponent.[2] 19 is the maximum number of fourth powers needed to sum up to any natural number, and in the context of Waring's problem, 19 is the fourth value of g(k). In addition, 19 is a Heegner number[3] and a centered hexagonal number.[4] 19 is also a centered triangular number,[5] being the smallest such number that is also prime. Moreover, there exists only one nontrivial normal magic hexagon: the one composed of 19 cells.

Science

• The atomic number of potassium.
• 19 years is very close to 235 lunations. See Metonic cycle.
• COVID-19 is the shortened name of Coronavirus disease 2019, the cause of the 2019–20 coronavirus outbreak.

Religion

Islam

• The number of angels guarding Hell ("Hellfire") ("Saqar") according to the Qur'an: "Over it are nineteen" (74:30), after which the Qur'an describes this number as being "a trial for those who disbelieve" (74:31), a sign for people of the scripture to be "convinced" (74:31) and that believers "will increase in faith" (74:31) due to it...
• The Number of Verse and Sura together in the Qur'an which announces Jesus son of Maryam's (Mary's) birth (Qur'an 19:19).
• A group called United Submitter International claim the Quran has mathematical structure based on the number 19. The gematrical value of WAHD = 5+1+8+4=18, Wahd means 'One' (God) to the first verse (1:1), known as Bas-malah, consists of 19 Arabic letters or the Quran consists of 114 (19x6) su-ras etc

Baha'i faith

In the Bábí and Bahá'í faiths, a group of 19 is called a Váhid, a Unity (Arabic: واحد wāhid, "one"). The numerical value of this word in the Abjad numeral system is 19.

• The Bahá'í calendar is structured such that a year contains 19 months of 19 days each (along with the intercalary period of Ayyám-i-Há), as well as a 19-year cycle and a 361-year (19x19) supercycle.
• The Báb and his disciples formed a group of 19.
• There were 19 Apostles of Bahá'u'lláh.

Music

• "19" is a 1985 song by Paul Hardcastle, including sampled soundbites taken from a documentary about the Vietnam War in which 19 is claimed to have been the average age of United States soldiers killed in the conflict.[6] The song was parodied by British satirist Rory Bremner under the pseudonym 'The Commentators,' as N-n-nineteen, Not Out, the title referring to the batting average of David Gower, the England cricket captain, during his side's risible performance against the West Indies in 1984 when they lost 5–0.

• "I Was Only Nineteen" by the Australian group Redgum reached number one on the Australian charts in 1983. In 2005 a hip hop version of the song was produced by The Herd.
• 19 is the name of Adele's 2008 debut album, so named since she was 19 years old at the time.
• "Hey Nineteen" is a song by American jazz rock band Steely Dan, on the 1980 album Gaucho.
• Nineteen has been used as an alternative to twelve for a division of the octave into equal parts. This idea goes back to Salinas in the sixteenth century, and is interesting in part because it gives a system of meantone tuning, being close to 1/3 comma meantone. See 19 equal temperament.
• Some organs use the 19th harmonic to approximate a minor third.

Literature

• Stephen King's eight-book epic The Dark Tower saga employs the number 19 in books The Dark Tower: The Gunslinger, The Dark Tower V: Wolves of the Calla, The Dark Tower VI: Song of Susannah, The Dark Tower VII: The Dark Tower, and The Wind Through the Keyhole as a mysterious and important number. They refer to the "ka-tet of 19", "Directive Nineteen," many names add up to 19, 19 seems to permeate every aspect of Roland and his traveler's lives. In addition, the number ends up being a powerful key.
• In Jodi Picoult's bestselling book Nineteen Minutes, the number 19 is referenced multiple times. It is most commonly referenced when referring to the main subject of the book, the school shooting rampage that took place over a span of 19 minutes.
• The novel "S." by Doug Dorst uses 19 and its multiples throughout. S is the 19th letter of the alphabet.

Games

A 19x19 Go board

• The game of Go is played on a grid of 19×19 lines (though variants can be played on grids of other sizes).
• Though the maximum score for a cribbage hand is 29, there is no combination of cards that adds up to 19 points. Many cribbage players, therefore, jokingly refer to a zero-point hand as "a 19 hand."
• In Ecuadorian card game "40", when counting the number of cards gathered in a hand, the limit is 19, after which the count starts at 6 and represents the points achieved during that hand.

Age 19

• This is the age of majority in some countries, Canadian provinces, and U.S. states.
• This is the minimum age that is legal to buy tobacco products in the states Alabama, Alaska, Utah and several counties in New York including Nassau, and Onondaga.[7]
• This is the minimum age at which one can drink and buy alcohol in Canada except for the provinces of Alberta, Manitoba, and Quebec where the drinking and purchase age of alcohol is 18.

In sports

• In golf, the '19th hole' is the clubhouse bar and in match play, if there is a tie after 18 holes, an extra hole(s) is played. In miniature golf it is an extra hole on which the winner earns an instant prize.

References

1. "Sloane's A000043 : Mersenne exponents". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
2. Guy, Richard; Unsolved Problems in Number Theory, p. 7 ISBN 1475717385
3. "Sloane's A003173 : Heegner numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
4. "Sloane's A003215 : Hex (or centered hexagonal) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
5. "Sloane's A125602 : Centered triangular numbers that are prime". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-31.
6. Roush, Gary (2008-06-02). "Statistics about the Vietnam War". Vietnam Helicopter Flight Crew Network. Archived from the original on 2009-12-07. Retrieved 2009-12-06. Assuming KIAs accurately represented age groups serving in Vietnam, the average age of an infantryman (MOS 11B) serving in Vietnam to be 19 years old is a myth, it is actually 22. None of the enlisted grades have an average age of less than 20.
7. Center for Health Improvement (2008-06-02). "Minimum Age Increase". Archived from the original on 2009-07-22. Retrieved 2004-06-30. In Alabama, Alaska, and Utah, 19 years is the minimum age for sale of tobacco products

External links

• Number 19 at the Database of Number Correlations
• Prime Curios for the number 19