19 (NUMBER)

19	10	9

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

Cardinal	19 nineteen
Ordinal	19th nineteenth
Numeral system	nonadecimal
Factorization	prime
Divisors	1, 19
Roman numeral	XIX
Roman numeral (Unicode)	XIX, xix
Binary	10011
Octal	23
Duodecimal	17
Hexadecimal	13

Contents

In mathematics

In science

In religion

In music

In other fields

Historical years

External links

In mathematics

Nineteen is the 8th smallest prime number. The sequence continues 23, 29, 31, 37... 19 is the seventh Mersenne prime exponent. 19 is the smallest Higgs prime for squares and cubes that has an index among Higgs primes that is less than its index among primes overall (because 17 is not a Higgs prime).
Every positive integer is the sum of at most nineteen fourth powers (see Waring's problem).
Nineteen is a centered triangular number, centered hexagonal number, and an octahedral number.
Nineteen is a Heegner number.
19 is the fourth alternating factorial, as it is equal to −(1!) + 2! + −(3!) + 4!
With respect to divisibility, nineteen has a very simple test: 19 divides 100''a'' + ''b'' if and only if it divides ''a'' + 4''b''.
In base 10, it is a Keith number, because it recurs in a Fibonacci-like sequence started from its base 10 digits: 1, 9, 10, 19... The decimal expansion of 1/19 has a period of maximum length: 18 digits. Regardless of the base, 19 is a strictly non-palindromic number. In Roman numerals, however, 19 is the largest palindromic prime.

In science

★ The atomic number of potassium.

In religion

★ The number of years in each cycle of the intercalated Hebrew calendar, in which 7 of the 19 years are leap years; it is used by Jews to calculate the time of observance of Jewish holidays.

★ The number of angels guarding Hell according to the Qur'an: "Over it is nineteen" (74:30)

★ The number of surat Maryam in the Qur'an

★ The number of letters in the Bismillah formula "In the name of God, Most Gracious, Most Merciful" in Arabic [1]

★ A number encoded in the Qur'an [2] as claimed by Dr. Rashad Khalifa, a biochemist from the USA, about the Qur'an [3]

★ The Bahá'í calendar is structured such that a year contains 19 months of 19 days each, as well as a 19-year cycle and a 361-year (19x19) supercycle. The Báb and his disciples formed a group of 19, and there were 19 Apostles of Bahá'u'lláh.

In music

"19" is a 1985 hit song by Paul Hardcastle, with a strong anti-war message, 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 (an assertion which is widely disputed). The song was parodied by British satirist Rory Bremner as ''N-n-nineteen, Not Out'', the title referring to the English cricket team's risible performance against the West Indies in the previous year.
With a similar name and anti-Vietnam War theme, ''I Was Only 19 (A Walk in the Light Green)'', 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, and was voted in at #18 in the 2005 Triple J Hottest 100 playlist.
Other songs with the number 19 in their titles:
: ''"Nineteen"'' by Buck-O-Nine
: ''"Nineteen"'' by Phil Lynott
: ''"Nineteen"'' by the Old 97's
: ''"Hey, Nineteen"'' by Steely Dan
: ''"19th Nervous Breakdown"'' by the Rolling Stones
: ''"Nineteen Forever"'' by Joe Jackson
: ''"I Got A Feeling (Just Nineteen)"'' by Eagles of Death Metal
: ''"Nineteen in Naples"'' by Jonathan Richman
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.
19 is also the title of Evan Yo's first album, because Evan was nineteen years old when the album released.

In other fields

'Nineteen' is

★ The nineteenth state to enter the Union of the United States was Indiana

★ Part of the name of a breakfast cereal: Product 19

★ The Soviet submarine K-19 was the first Soviet nuclear ballistic submarine

★ I-19 is the designation for a US interstate highway in Arizona

★ the height, in feet, of the statues of Abraham Lincoln and Thomas Jefferson in their respective memorials.

★ 19 years is very close to 235 lunations. See Metonic cycle

★ A significant recurring number (which comes to denote a sense of unreality and foreboding) in the ''Dark Tower'' novels by author Stephen King

★ In golf the "19th hole" is the clubhouse bar. In miniature golf it is an extra hole on which the winner earns an instant prize

★ A number encoded in Chemistry as claimed by Dr. Peter Plichta, a German chemist [4]. Also see [5] for Plichta's claimed code-19 in chemistry

★ The retired football jersey number of Hall of Famers Johnny Unitas and Lance Alworth

★ The retired baseball jersey number of Baseball Hall of Fame members Robin Yount and Tony Gwynn.

★ The retired basketball jersey number of Willis Reed.

★ The retired hockey jersey number of Steve Yzerman.

★ The number of Colorado Avalanche center and captain Joe Sakic

★ 19 x 19 is also the standard size of a Go Board

★ It is not possible to earn a score of 19 in a single hand of cribbage

Historical years

'A.D. 19', 19 B.C., 1919, 2019, etc.

External links

★ 19.ORG

★ Prime Curios for the number 19

★ Agir XIX

★ Code 19 Deceit