20 (عدد)

20 (عشرون) هو عدد صحيح يلي العدد 19 ويسبق العدد 21 وهو عدد طبيعي موجب. العدد ليس أولي لكنه يقسم على الأرقام 1، 2، 4، 5، 10، ونفسه بدون باقي.

← 19 20 21 →
← 20 21 22 23 24 25 26 27 28 29 → قائمة الأعداد الأعداد الصحيحة ← 0 10 20 30 40 50 60 70 80 90 →
كمي
ترتيبي	20 ()
نظام العد	vigesimal
التحليل لعوامل	22× 5
القواسم	1, 2, 4, 5, 10, 20
العدد اليوناني	Κ´
العدد الروماني	XX
ثنائي	101002
ثلاثي	2023
رباعي	1104
خماسي	405
سداسي	326
ثماني	248
اثنا عشري	1812
ستة عشري	1416
عشريني	1020
أساس 36	K36

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 في الرياضيات

An icosahedron has 20 faces.

• 20 is a pronic number.
• 20 is a tetrahedral number as 1, 4, 10, 20.
• 20 is the basis for vigesimal number systems.
• 20 is the third composite number to be the product of a squared prime and a prime, and also the second member of the (2²)q family in this form.
• 20 is the smallest primitive abundant number.
• An icosahedron has 20 faces. A dodecahedron has 20 vertices.
• 20 can be written as the sum of three Fibonacci numbers uniquely, i.e. 20 = 13 + 5 + 2.
• 20 is the number of moves (quarter or half turns) required to optimally solve a Rubik's Cube in the worst case.
• 20 is the number of parallelogram polyominoes with 5 cells.

 في العلوم

• The atomic number of calcium.
• The third magic number in physics.
• The International Astronomical Union shower number for Coma Berenicids.

 في علم الأحياء

• The number of proteinogenic amino acids that are encoded by the standard genetic code.
• In some countries, 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". (Note that this applies only to countries using the Imperial system. The metric equivalent is 6/6.) 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".

 كعدد غير محدد

• A 'score' is a group of 20 (often used in combination with a cardinal number, i.e. fourscore to mean 80), but also often used as an indefinite number (e.g. the newspaper headline "Scores of Typhoon Survivors Flown to Manila").

 في الرياضة

For retired sports figures who wore this number, see List of retired numbers#20

A standard dartboard is laid out as 20 sectors.

• Twenty20 is a form of limited overs cricket where each team plays only 20 overs.
• A standard dartboard is laid out as 20 sectors.
• The Kentucky Derby currently has a maximum field of 20 horses.
• In rugby union, 20 national teams currently qualify for each edition of the men's Rugby World Cup.
• In chess, 20 is the number of legal moves for each player in the starting position.
• In Australian rules football, most games consist of four 20-minute quarters.
• Under NCAA men's basketball rules, games consist of 20-minute halves.
• Ice hockey games are played in three 20-minute periods.

 العمر 20

• In many disciplines of developmental psychology, adulthood starts at age 20.
• Formerly the age of majority in Japan and in Japanese tradition.
• Age 20 is the age at which Levites in the time of King David were allowed "to do the work for the service of the house of the Lord", the Temple in Jerusalem (see First Chronicles Chapter 23, verses 24 and 27). In the time of Ezra and Nehemiah, following the Babylonian captivity, it was Levites from the age of 20 upwards who were assigned "to oversee the work of the house of the LORD" (Ezra Chapter 3, verse 8).

 الموسيقى

Albums
20	Related	Twenty	Related
Harry Connick, Jr.	20+ Baron Rojo	Bob Baldwin	Twenty+ All-4-One
Orbital	20% Maria Bamford	Boyz II Men	20 [Twenty] FT Island
TLC		Chicane
Jars of Clay		Robert Cray
Africa Unite		Jebediah
Kate Rusby		Lynyrd Skynyrd
Hyukoh		Taking Back Sunday
Pastora Soler
The Gift
Sofa Surfers
Capo Plaza
John Dahlbäck

Songs
20	Related	Twenty
Ebbo Kraan	#20 - Fat Tuesday	The Rippingtons
Seventeen	#20 - Aphex Twin
Janet Jackson	#20 - Tony Wilson Sextet
Gorky's Zygotic Mynci	#20 - David Paul Mesler
Covenant	$20 - Low (band)
Car 44	$20 - Qwiksand
Karma to Burn	$20 - Norman Palm
Ike Yard	20% - Furyus
Noah Stone	20% - Banfi
Alec Empire	-20 - Brendon Moeller
Beans	-20 - Mr. 76ix
Damián Schwartz	20 (intro) - Janet Jackson
Anarchestra	20 (Palbarrio) - El Barrio

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 في الحقول الأخرى

• +20 is the code for international direct dial phone calls to Egypt.
• CB slang for a place, being short for the ten-code "10–20" meaning "What is your location?"
• 20/20 is a primetime newsmagazine program on ABC, which in turn is taken from the expression for normal eyesight (20/20 vision).
• 020 is the ISO 3166-1 numeric 3 digit country code for Andorra.
• The UIC Country Code for Russia identifying member countries of the International Union of Railways (UIC).
• 20 is the value of the letter J when computing the check digit in the serial number of an intermodal (shipping) container, as defined by ISO 6346.
• In Hebrew numerals, the letter Kaph (כ) represents twenty; see also gematria, the Hebrew system of numerology. Similarly the Arabic letter kāf (ك) represents twenty in the Abjad numerals.
• The number of questions in the game Twenty Questions.

 انظر أيضاً

• List of highways numbered 20

 وصلات خارحية

• Media related to 20 (عدد) at Wikimedia Commons