19 (number)

"XIX" redirects here. For other uses, see 19 (disambiguation).

← 18 19 20 →
← 10 11 12 13 14 15 16 17 18 19 → List of numbers — Integers ← 0 10 20 30 40 50 60 70 80 90 →
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

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

Mathematics

19 is a centered triangular number

• 19 is the 8th prime number, the seventh Mersenne prime exponent, a Heegner number, a deficient number, the second Keith number (and also the first Keith prime), and the second base-10 repunit prime exponent (for the number 1111111111111111111).
• 19 is a centered triangular number as well as a centered hexagonal number.
• 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).
• There are infinitely many finite-volume Vinberg polytopes up through dimension 19.
• The only nontrivial normal magic hexagon is composed of 19 cells.

Science

The James Webb Space Telescope features a design of 19 hexagons.

• 19 is 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 global pandemic that began in 2019.
• The James Webb Space Telescope's optical elements are in an array of 19 hexagons, wherein 18 segmented primary mirrors focus light into a centered secondary mirror situated above the collecting mirrors, that in-turn reflects back onto the telescope's central imagers. It is a shape akin to the order-3 magic hexagon.

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 = 6+1+8+4=19, 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) surat etc.

Baháʼí faith

In the Bábí and Baháʼí 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 Baháʼí 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.

Celtic paganism

19 is a sacred number of the goddess Brigid because it is said to represent the 19-year cycle of the Great Celtic Year and the amount of time it takes the Moon to coincide with the winter solstice.

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. 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 the base version of Settlers of Catan there are 19 hexagonal pieces that can be randomly or intentionally placed to form the board.

Age 19

• In four countries, 19 is the age of majority.
• In two countries, 19 is the minimum legal drinking age.
• In three countries, 19 is the minimum legal smoking age.

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.

Other fields

• The 19th Amendment to the United States Constitution gave American women the right to vote.
• The Vietnam War spanned over 19 years, from November 1955 to April 1975.

External links

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