19 (number)
From Wikipedia, the free encyclopedia.
19 (nineteen) is the natural number following 18 and preceding 20.
| |||
| Cardinal | nineteen | ||
| Ordinal | nineteenth | ||
| Factorization | prime | ||
| Roman numeral | XIX | ||
| Binary | 10011 | ||
| Hexadecimal | 13 | ||
| Table of contents |
|
2 In music 3 In other fields 4 External link |
In mathematics
Nineteen is the 8th smallest prime number. The sequence continues 23, 29, 31, 37...
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 hexagonal number, and an octahedral number.
Every positive integer is the sum of at most nineteen fourth powers.
The decimal expansion of 1/19 has a period of maximum length: 18 digits.
Nineteen is a Heegner number.
Any positive integer can be expressed by at most a sum of 19 4th powers.
In music
"19" is a 1985 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.
In other fields
Nineteen is
- The atomic number of potassium.
- 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.
- Historical years: 19 A.D., 19 B.C, or 1919
External link