20 (number)
From Free net encyclopedia
20 (twenty) is the natural number following 19 and preceding 21. A group of twenty units is often referred to as a score.
Abraham Lincoln began the Gettysburg address in 1863 with the sentence: "Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal." Lincoln might have cut it short and said, somewhat less memorably: "The Declaration of Independence was issued 87 years ago in 1776."
| Cardinal | 20 twenty |
| Ordinal | 20th twentieth |
| Numeral system | vigesimal |
| Factorization | <math>2^2\cdot 5</math> |
| Roman numeral | XX |
| Binary | 10100 |
| Duodecimal | 18 |
| Hexadecimal | 14 |
| Vigesimal | 10 |
| Hebrew | כ (Kaf) |
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In mathematics
Twenty is a composite number, its proper divisors being 1, 2, 4, 5 and 10. It is also the sum of the first four triangular numbers, making it a tetrahedral number. 20 is the smallest abundant number that is not a multiple of 3. It is a Harshad number and a self number.
20 is the total number of digits on the human body, which makes it a possible candidate for a numeral system.
Twenty is used as a radix for vigesimal number systems. In the old UK currency system, there were twenty shillings in a pound.
A polyhedron with twenty faces is an icosahedron.
Twenty is the first number in an early Indian magic square of order 3.
In science
- The atomic number of calcium.
- The third Magic number (physics).
Astronomy
- Messier object M20, a magnitude 5.0 nebula/open cluster in the constellation Sagittarius, also known as the Trifid Nebula.
- The New General Catalogue object NGC 20, a spiral galaxy in the constellation Andromeda
- The Saros number of the solar eclipse series which began on -2286 June 5 and ended on -1006 July 13. The duration of Saros series 20 was 1280.1 years, and it contained 72 solar eclipses.
- The Saros number of the lunar eclipse series which began on -1966 March 25 and ended on -668 May 12. The duration of Saros series 20 was 1298.1 years, and it contained 73 lunar eclipses.
Biology
- The number of proteinogenic amino acids that are encoded by the standard genetic code.
- The number 20 is used as an index in measuring visual acuity. 20/20 indicates normal vision at 20 feet, although it is commonly used to mean "perfect vision". When someone is able to see only after an event how things turned out, that person is often said to have had "20/20 hindsight".
In sports
- The retired number of former baseball stars Frank Robinson and Mike Schmidt.
- 20 is the number of Tony Stewart's 2-time winning NASCAR NEXTEL Cup Series car.
In other fields
Image:Tv sesame street 20 chairs.jpg
- In a game of chess both players have 20 first moves from which to choose.
- Twenty questions is a popular party game.
- Twenty is the age of majority in Japanese tradition. Someone who is exactly twenty years old is described as hatachi.
- The "Twenty Year Curse" refers to the pattern of the president of the United States elected every twenty years starting with 1840 to die in office. This pattern failed when Reagan survived his time in office.
- Bands with the number twenty in their name include matchbox twenty and 20goto10, a synthpop band whose website is www.20goto10.us.
- A 20-minute-long entertainment program shown before some films playing in United Artists movie theaters is called "The Twenty" (spelled "The 20wenty").
- A curious survival from the Celtic languages is preserved in folklore from the north of England; this is called the "Lincolnshire Score" or the Shepherd's Score. This is a tally that counts twenty units using this jingle. It is or was sometimes used to count sheep.
- Yan, tan, tethera, pethera, pimp,
- sethera, lethera, hovera, dovera, dick,
- yanadick, tanadick, tetheradick, petheradick, bumfit,
- yanabumfit, tanabumfit, tetherabumfit, petherabumfit, jiggit.
- There are several other variants, but all have similar words for at least the first five units, and the principle of counting 16 to 19 by adding ones to 15, as is done in some Celtic dialects. To compare the Score with Celtic language numbers, see Numbers in various languages.
- The ordinal adjective is vicenary.
- 20/20 is a late-night newsmagazine program on the ABC network, that has been hosted by Barbara Walters, Hugh Downs, Elizabeth Vargas, and others.
20 is:
- The code for international direct dial phone calls to Egypt.
- Twenty, a village in Lincolnshire
- In the United States Constitution, $20 is the threshold value of civil disputes above which the right to trial by jury is preserved.
- The denomination of U.S. dollar with Andrew Jackson's portrait.
- The designation of Interstate 20, a freeway that runs from Texas to South Carolina.
- Twenty, a 1997 album by Lynyrd Skynyrd.
- Historical years: 20 A.D., 20 B.C., or 1920
- CB radio jargon for "a place", being short for "10-20", used in reference to a person or object's location.
- One of the TCP/IP ports used for File Transfer Protocolca:Vint
da:20 (tal) de:Zwanzig es:Veinte eo:Dudek fr:20 (nombre) ko:20 ia:20 it:Venti he:20 (מספר) lt:20 (skaičius) nah:Cempohualli nl:20 (getal) ja:20 nap:Vinte no:20 (tall) pl:20 (liczba) pt:Vinte ru:20 (число) sl:20 (število) sv:20 (tal) th:20 yo:Õgún zh:20