# 10

Last updated on 26 October 2017

10 (ten /ˈtɛn/ ()) is an even natural number following 9 and preceding 11. Ten is the base of the decimal numeral system, by far the most common system of denoting numbers in both spoken and written language. The reason for the choice of ten is assumed to be that humans have ten fingers (digits).

 11 → 10 ← 9 ten 10th (tenth) decimal 2 × 5 1, 2, 5, 10 Ι´ X X, x deca-/deka- deci- 10102 1013 224 205 146 128 A12 A16 A20 A36 十，拾 י (Yod) ១០ 십 ௰ ๑๐ १० ১০ ١٠

## Common usage and derived terms

• A collection of ten items (most often ten years) is called a decade.
• The ordinal adjective is decimal; the distributive adjective is denary.
• Increasing a quantity by one order of magnitude is most widely understood to mean multiplying the quantity by ten.
• To reduce something by one tenth is to decimate. (In ancient Rome, the killing of one in ten soldiers in a cohort was the punishment for cowardice or mutiny; or, one-tenth of the able-bodied men in a village as a form of retribution, thus causing a labor shortage and threat of starvation in agrarian societies.)
• A theoretical highest number in topics that require a rating ("a mark out of ten"), by contrast having 0 or 1 as the lowest number, and 5 being average.

## In mathematics

• Ten is the second discrete semiprime (2 × 5) and the second member of the (2 × q) discrete semiprime family. Ten has an aliquot sum σ(n) of 8 and is accordingly the first discrete semiprime to be in deficit. All subsequent discrete semiprimes are in deficit. The aliquot sequence for 10 comprises five members (10,8,7,1,0) with this number being the second composite member of the 7-aliquot tree.
• Ten is the smallest semiprime that is the sum of all the distinct prime numbers from its lower factor through its higher factor (10 = 2 + 3 + 5 = 2 . 5) Only three other small semiprimes (39, 155, and 371) share this attribute.
• Ten is the sum of the first three prime numbers, of the four first positive integers (1 + 2 + 3 + 4), of the square of the two first odd numbers and also of the first four factorials (0! + 1! + 2! + 3!). Ten is the eighth Perrin number, preceded in the sequence by 5, 5, 7.
• Ten is the smallest number whose status as a possible friendly number is unknown.

### In numeral systems

#### Decimal system

As is the case for any base in its system, ten is the first two-digit number in decimal and thus the lowest number where the position of a numeral affects its value. Any integer written in the decimal system can be multiplied by ten by adding a zero to the end (e.g. 855 × 10 = 8550).

#### Roman numerals

The Roman numeral for ten is X (which looks like two Vs [the Roman numeral for 5] put together); it is thought that the V for five is derived from an open hand (five digits displayed), and X for ten from both hands. Incidentally, the Chinese word numeral for ten, is also a cross: .

#### Positional numeral systems other than decimal

The digit '1' followed by '0' is how the value of p is written in base p. (E.g. 16 in hexadecimal is 10.)

Representation of 10 in other bases
Base Numeral system Number
1 unary **********
2 binary 1010
3 ternary 101
4 quaternary 22
5 quinary 20
6 senary 14
7 septenary 13
8 octal 12
9 novenary 11
10 decimal 10
12 duodecimal X

## List of basic calculations

Multiplication 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 25 50 100 1000
10 × x 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 250 500 1000 10000
Division 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
10 ÷ x 10 5 3.3 2.5 2 1.6 1.428571 1.25 1.1 1 0.90 0.83 0.769230 0.714285 0.6
x ÷ 10 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5
Exponentiation 1 2 3 4 5 6 7 8 9 10
10x 10 100 1000 10000 100000 1000000 10000000 100000000 1000000000 10000000000
x10 1 1024 59049 1048576 9765625 60466176 282475249 1073741824 3486784401 10000000000

## In science

The SI prefix for 10 is "deca-".

The meaning "10" is part of the following terms:

• decapoda, an order of crustaceans with ten feet
• decane, a hydrocarbon with 10 carbon atoms

Also, the number 10 plays a role in the following:

The metric system is based on the number 10, so converting units is done by adding or removing zeros (e.g. 1 centimeter = 10 millimeters, 1 decimeter = 10 centimeters, 1 meter = 100 centimeters, 1 dekameter = 10 meters, 1 kilometer = 1,000 meters).

## In money

Most countries issue coins and bills with a denomination of 10 (See e.g. 10 dollar note). Of these, the U.S. dime, with the value of ten cents, or one tenth of a dollar, derives its name from the meaning "one-tenth" − see Dime (United States coin)#Denomination history and etymology.

## In music

• The interval of a major tenth is an octave plus a major third.
• The interval of a minor tenth is an octave plus a minor third.
• The title of quite a few albums. See Ten (album).
• "Ten lords a-leaping" is the gift on the tenth day of Christmas in the carol "The Twelve Days of Christmas".

## In sports and games

• Decathlon is a combined event in athletics consisting of ten track and field events.
• In association football, the number 10 is traditionally worn by the team's advanced playmaker. This use has led to "Number 10" becoming a synonym for the player in that particular role, even if he or she does not wear that number.[8]
• In auto racing, driving a car at ten-tenths is driving as fast as possible, on the limit.
• In blackjack, the Ten, Jack, Queen and King are all worth 10 points.
• In boxing, if the referees counts to 10 whether the boxer is unconscious or not, it will declare a winner by knockout.
• In most rugby league competitions, the number 10 is worn by one of the two starting props. One exception to this rule is the European Super League, which uses static squad numbering.
• In rugby union, the starting fly-half wears the 10 shirt.
• In ten-pin bowling, 10 pins are arranged in a triangular pattern and there are 10 frames per game.

## In other fields

10 playing cards of all four suits
• Blake Edwards' 1979 movie 10.
• Series on HBO entitled 1st & Ten which aired between December 1984 and January 1991.
• Series on ESPN and ESPN2 entitled 1st and 10 which launched on ESPN in October 2003 to 2008 and moved to ESPN2 from 2008 to present.
• In astrology, Capricorn is the 10th astrological sign of the Zodiac.
• In Chinese astrology, the 10 Heavenly Stems, refer to a cyclic number system that is used also for time reckoning.
• A 1977 short documentary film Powers of Ten depicts the relative scale of the Universe in factors of ten (orders of magnitude).
• CBS has a game show called Power of 10, where the player's prize goes up and down by either the previous or next power of ten.
• "Ten Chances" is one of the pricing games on The Price is Right.
• There are ten official inkblots in the Rorschach inkblot test.
• The traditional Snellen chart uses 10 different letters.
• Ten is an Australian television network. The Sydney member of the network has the three-letter call-sign TEN and used to broadcast in analogue on VHF Channel 10.
• Number Ten (also called Ella) is a character in the book series Lorien Legacies. The sixth book, The Fate of Ten, is named after her.
• The ten-code may be used in law enforcement brevity communications.

Ten is:

• Mathematics portal

## References

1. ^ "Sloane's A005278 : Noncototients". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
2. ^ "Sloane's A001107 : 10-gonal (or decagonal) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
3. ^ "Sloane's A005448 : Centered triangular numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
4. ^ "Sloane's A000292 : Tetrahedral numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-06-01.
5. ^
6. ^
7. ^ [1] Archived February 23, 2006, at the Wayback Machine.
8. ^ Khalil Garriot (21 June 2014). "Mystery solved: Why do the best soccer players wear No. 10?". Yahoo. Retrieved 19 May 2015.

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