19 (number)

"Nineteen" redirects here. For other uses, see 19 (disambiguation).
18 19 20
Cardinal nineteen
Ordinal 19th
(nineteenth)
Numeral system nonadecimal
Factorization prime
Divisors 1, 19
Roman numeral XIX
Binary 100112
Ternary 2013
Quaternary 1034
Quinary 345
Senary 316
Octal 238
Duodecimal 1712
Hexadecimal 1316
Vigesimal J20
Base 36 J36

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

In English speech, the numbers 19 and 90 are often confused, as sounding very similar. When carefully enunciated, they differ in which syllable is stressed: 19 /nnˈtn/ vs 90 /ˈnnti/. However, in dates such as 1999, and when contrasting numbers in the teens and when counting, such as 17, 18, 19, the stress shifts to the first syllable: 19 /ˈnntn/.

Mathematics

19 is the 8th prime number. The sequence continues 23, 29, 31, 37, ... .

19 is the seventh Mersenne prime exponent.

19 is the fifth happy number and the third happy prime.

19 is the aliquot sum of two odd discrete semiprimes, 65 and 77 and is the base of the 19-aliquot tree.

19 is the lowest prime centered triangular number, a centered hexagonal number and a Heegner number.

The only non-trivial normal magic hexagon contains 19 hexagons (the other being 1).

19 is the first number with more than one digit that can be written from base 2 to base 19 using only the digits 0 to 9; the other number is 20.[1]

Technology

19 is The TCP/IP port used for chargen.

Science

Religion

Islam

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.

Music

Literature

Games

A 19x19 Go board

Age 19

In sports

Other fields

References

  1. Sequence A131646 in The On-Line Encyclopedia of Integer Sequences
  2. Roush, Gary (2008-06-02). "Statistics about the Vietnam War". Vietnam Helicopter Flight Crew Network. Archived from the original on 2009-12-06. 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.
  3. 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

Wikimedia Commons has media related to 19 (number).
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