10 11 → Ordinal 10th (tenth) Factorization 2 × 5 | Cardinal ten Numeral system decimal Divisors 1, 2, 5, 10 | |

**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).

## Contents

## Common usage and derived terms

*decimal*; the distributive adjective is

*denary*.

*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.)

## In mathematics

Ten is a composite number, its proper divisors being 1, 2 and 5. Ten is the smallest noncototient, a number that cannot be expressed as the difference between any integer and the total number of coprimes below it.

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.

It is the aliquot sum of only one number the discrete semiprime 14.

Ten is a semi-meandric number.

Ten is the sum of the first three prime numbers, of the four first numbers (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.

A polygon with ten sides is a decagon, and 10 is a decagonal number. Because 10 is the product of a power of 2 (namely 2^{1}) with nothing but distinct Fermat primes (specifically 5), a regular decagon is a constructible polygon.

Ten is also a triangular number, a centered triangular number, and a tetrahedral number.

Ten is the number of *n* queens problem solutions for *n* = 5.

Ten is the smallest number whose status as a possible friendly number is unknown.

## 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 V's [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: 十.

## 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.)

Properties:

## In science

The SI prefix for 10 is "deca-".

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

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).

## Astronomy

## In religion and philosophy

*Maaser Ani*). From this verse and from an earlier verse (Deut. 14:22) there derives a practice for Jews to give one-tenth of all earnings to the poor.

## 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

**Ten (album)**.

## In sports and games

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

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

The jersey number 10 has been retired by several North American sports teams in honor of past playing greats or other key figures, including Major League Baseball, the NBA, the NFL, and the NHL.

## In technology

## In other fields

*10*.

*1st & Ten*which aired between December 1984 and January 1991.

*1st and 10*which launched on ESPN in October 2003 to 2008 and moved to ESPN2 from 2008 to present.

*Powers of Ten*depicts the relative scale of the Universe in factors of ten (orders of magnitude).

*Power of 10*, where the player's prize goes up and down by either the previous or next power of ten.

*The Price is Right*.

*Lorien Legacies*. The sixth book,

*The Fate of Ten*, is named after her.

**Ten** is:

## In literature

*Naruto*universe that was defeated by the Sage of The Six Paths in the past, summoned by Nagato and absorbed and reabsorbed into Obito and Madaras' bodies after becoming its jinchūriki, and sealed away inside Kaguya Ōtsutsukis' dimension by Naruto and Sasuke after her being defeated and sealed away by the hands of the three Squad Seven members: Naruto, Sasuke and Sakura respectively.

*Digimon Frontier*Seraphimon, one of the Celestial Digimon and a member of the Miracle 4 in the digital world, has ten long yellow-golden wings.