# 8 number

 0 10 20 30 40 50 60 70 80 90 >> Cardinal 8 eight Ordinal 8th eighth Numeral system octal Factorization $\displaystyle 2^3$ Divisors 1, 2, 4, 8 Roman numeral VIII Unicode representation of Roman numeral Ⅷ, ⅷ prefixes octa-/oct- (from Greek) octo-/oct- (from Latin) Binary 1000 Octal 10 Duodecimal 8 Hexadecimal 8 Hebrew ח (Het)

8 (eight) is the natural number following 7 and preceding 9.

The SI prefix for 10008 is yotta (Y), and for its reciprocal yocto (y).

## In mathematics

It is a composite number, its proper divisors being 1, 2, and 4. Eight is a power of two, being 23, or two cubed.

8 is the base of the octal number system, which is mostly used with computers. In octal, one digit represents three bits. In modern computers, a byte is a grouping of eight bits, also called an octet.

The number 8 is a Fibonacci number, being 3 plus 5. The next Fibonacci number is 13. 8 is also a Harshad number.

In binary code eight is 1000; in ternary code eight is 22; in quaternary numeral system code eight is 20; in quinary eight is 13; in senary eight is 12; in septenary eight is 11; in octal eight is 10; in novenary code and all codes above (such as decimal and hexadecimal) eight is 8. In Roman numerals eight is VIII.

A polygon with eight sides is an octagon. Figurate numbers representing octagons (including eight) are called octagonal numbers. A polyhedron with eight faces is an octahedron.

Sphenic numbers always have exactly eight divisors.

8 is the dimension of the octonions and is the highest possible dimension of a normed division algebra.

## The Arabic glyph

In the beginning, various groups in India wrote 8 more or less in one stroke as a curve that looks like an uppercase H with the bottom half of the left line and the upper half of the right line removed. At one point this glyph came close to looking like our modern 5. With the western Ghubar Arabs, the similarity of the glyph to 5 was banished by connecting the beginning and the end of stroke together, and it was only a matter of the Europeans rounding the glyph that led to our modern 8.

In fonts with text figures, 8 usually has an ascender, for example, File:TextFigs148.png.

## In science

### In astronomy

Messier object M8, a magnitude 5.0 nebula in the constellation Sagittarius.
The New General Catalogue object NGC 8, a double star in the constellation Pegasus
The Saros number of the solar eclipse series which began on 2579 BCE March 7 and ended on 1281 BCE April 26. The duration of Saros series 8 was 1298.1 years, and it contained 73 solar eclipses.
The Saros number of the lunar eclipse series which began on 2512 BCE July 27 and ended on 961 BCE February 13. The duration of Saros series 7 was 1550.6 years, and it contained 87 lunar eclipses.

## In music

• A note played for one-eighth the duration of a whole note is called an eighth note, or quaver.

## In technology

• Many (mostly historic) computer architectures are eight-bit, among them the Nintendo Entertainment System.
• On most phones, the 8 key is associated with the letters T, U, and V, but on the BlackBerry it is the key for B and N.

## In other fields

• "Eight maids a-milking" is the gift on the eighth day of Christmas in the "Twelve days of Christmas" carol.
• I-8 is the designation of the US interstate highway that runs from San Diego, California to Casa Grande, Arizona.
• Eight is the number of categories the VALS system uses to classify consumer groups, and the number of categories used by Fallon-McElligott's system for teen marketing.
• There is a brand of chocolates filled with peppermint-flavoured cream called "After Eight", referring to the time 8 p.m.
• There are eight vegetables in V8 juice.
• The ordinal adjective is octonary.
• A euphemism for masturbation within a small group of gamers who coined the expression (placing "masturbation" in the eighth space in a list of instructions, as a joke).
• 8 apparations appear to Macbeth in Act 4 scene 1 of Shakespeare's Macbeth as representations of the 8 decendents of Banquo who will be king.