Home > 19 (number)

1 In mathematics

Nineteen is the 8th smallest prime number. The sequence continues 23, 29, 31, 37... 19 is the seventh Mersenne prime exponent.

It is also a Keith number, because it recurs in a Fibonacci-like sequence started from its base 10 digits: 1, 9, 10, 19...

With respect to divisibility, nineteen has a very simple test: 19 divides 100×a+b if and only if it divides a+4×b.

Nineteen is a centered triangular number, centered hexagonal numberA centered hexagonal number or hex number is a centered figurate number that represents a hexagon with a dot in the center and all other dots surrounding the center dot in successive hexagonal layers. The centered hexagonal number for n is given by the fo, and an octahedral numberAn octahedral number is a figurate number that represents an octahedron, or two pyramids placed together, one upside-down underneath the other. The octahedral number for n can be obtained by adding the n-1 and n square pyramidal numbers together, or by us.

Every positiveIn common usage positive is sometimes used in affirmation, as a synonym for "yes" or to express "certainty". In mathematics, a number is called positive if it is bigger than zero. See negative and non-negative numbers. In functional analysis, a bounded li integerThe integers consist of the positive natural numbers (1, 2, 3, …) the negative natural numbers (−1, −2, −3,. and the number zero. The set of all integers is usually denoted in mathematics by Z (or Z in blackboard bold, ), which st is the sum of at most nineteen fourth powerThe concept of power occurs in multiple areas. Physics Power (physics is the amount of work done per unit of time. Electric power Social Power (sociology) Political power Reserve power Power (international), the ability of national states to influence ors.

The decimal expansion of 1/19 has a period of maximum length: 18 digits.

Nineteen is a Heegner numberIn number theory, a Heegner number is a positive integer n such that the quadratic field Q √ n has class number 1. Equivalently, its ring of integers has unique factorization. See Stark-Heegner theorem for the proof that such n that are square free.

2 In music

"19" is a 1985See also 1984 in music, other events of 1985, 1986 in music, 1980s in music and the list of 'years in music' Events January 28 Various artists, including Ray Charles, Bob Dylan, Michael Jackson, Billy Joel, Cyndi Lauper, Willie Nelson, Lionel Richie, Smok hit song by Paul Hardcastle, with a strong anti-war message, based on 19 being the average age of soldiers in the Vietnam war.

Other songs with the number in their titles include "Nineteen" by the Old 97's and "Hey, Nineteen" by Steely Dan.