9 number: Encyclopedia - 9 number

9 (number)

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List of numbers -- Integers

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nona- (from Latin)

9 (nine) is the natural number following 8 and preceding 10.

9 number - In mathematics

Nine is a composite number, its proper divisors being 1 and 3. It is 3 times 3 and hence the third square number. 9 is a Motzkin number.

In base 10 a number is evenly divisible by nine if and only if the iterative sum of its digits reduces to 9. A simple way of saying this is that if you multiply nine by any whole number, and repeatedly add the digits of the answer until it's just one digit, you will end up with nine:

• 2*9=18 (1+8=9)
• 3*9=27 (2+7=9)
• 9*9=81 (8+1=9)
• 234*9=2106 (2+1+0+6=9)
• 578329*9=5204961 (5+2+0+4+9+6+1=27 (2+7=9))

The only other number with this property is three. In base N, the divisors of N − 1 have this property. Another consequence of 9 being 10 − 1, is that it is also a Kaprekar number.

Every prime in a Cunningham chain of the first kind with a length of 4 or greater is congruent to 9 mod 10 (the only exception being the chain 2, 5, 11, 23, 47).

Since , 9 is an exponential factorial.

In probability, the nine is a logarithmic measure of probability of an event, defined as the negative of the base-10 logarithm of the probability of the event's complement. For example, an event that is 99% likely to occur has an unlikelihood of 1% or 0.01, which amounts to −log₁₀ 0.01 = 2 nines of probability. Zero probability gives zero nines (−log₁₀ 1 = 0). The purity of chemicals (see Nine (purity)), the effectivity of processes, the availability of systems etc. can similarly be expressed in nines. For example, "five nines" (99.999%) availability implies a total downtime of no more than five minutes per year. This measure can be confusing, a fact which is discussed in The Myth of the Nines.

Six recurring nines appear in the decimal places 762 through 767 of pi. This is known as the Feynman point (see also MathWorld).

A polygon with nine sides is called an enneagon (technically) or nonagon (in common usage). A group of nine of anything is called an ennead.

9 number - In numeral systems

9 number - The Arabic glyph

In the beginning, various Indians wrote 9 in a way that pretty much looks like our modern closing question mark, but dotless. The Kshtrapa, Andhra and Gupta started curving the bottom vertical line coming up with a 3-look-alike. The Nagari continued the bottom stroke to make a circle to enclose the 3-look-alike, in much the same way that the @ character encircles a lowercase a. As time went on, the enclosing circle became bigger and its line continued beyond the circle downwards, and the 3-look-alike became smaller. Soon, all that was left of the 3-look-alike was a squiggle. The Arabs simply connected that squiggle to the downward stroke at the middle, and all the Europeans did to the glyph was purely cosmetic.

In fonts with text figures, 9 usually has a descender, for example, .

See also: Hindu-Arabic numeral system.

9 number - As lucky or unlucky number

Nine (九 pinyin jiǔ) is considered a good number in Chinese culture because it sounds the same as the word "longlasting" (久 pinyin jiǔ). The Japanese consider 9 to be unlucky, however.

According to Anton Szandor LaVey, as written on his book The Satanic Rituals, 9 is the number of Satan.

In Thai language, the word for nine, 'gao', is the same as the verb for 'to develop or progress'. Important Buddhist rituals usually involve nine monks.

9 number - In science

• Nine is the atomic number of fluorine

In astronomy,

9 number - In music

In music theory a ninth is the ninth note of a musical scale or the interval between the first note and the ninth. A ninth chord is a chord with a ninth.

Ludwig van Beethoven, Franz Schubert, Anton Bruckner, and Ralph Vaughan Williams wrote nine symphonies. After Beethoven died leaving his Tenth Symphony unfinished, many composers were superstitious about writing Ninth Symphonies for the rest of the nineteenth century. Gustav Mahler tried to "cheat death" by writing an orchestral song cycle entitled Das Lied von der Erde instead of an instrumental Ninth Symphony. Afterwards he wrote a work called Ninth Symphony, but thought of it as his Tenth. He died with his Tenth (or, strictly and in his mind, his Eleventh) unfinished. Perhaps Antonín Dvořák was also superstitious about the number nine, because he wrote no symphonies after his New World Symphony, which is nowadays considered his Ninth, but which he thought of was his Eighth because he considered the score of his early C minor Symphony lost forever. He lived for seven more years. In the twentieth century, a handful of composers, such as Dmitri Shostakovich, have written a Ninth Symphony and lived to write more.

Nine is the number of Valkyries in Richard Wagner's Die Walküre.

Bands with the number nine in their name include Stroke 9, Nine Days, Nine Inch Nails and Revolution 9.

In pop music, the song "Love Potion #9" was written by Jerry Leiber and Mike Stoller (who also wrote "Riot in Cell Block No. 9"), and became a hit for The Searchers in 1965. The Beatles released a song called "Revolution 9" which appears on The White Album (more properly known as The Beatles); its principle vocal feature is a voice repeating, "Number nine...number nine...number nine..." John Lennon, the primary composer of "Revolution 9", also released a solo recording entitled "#9 Dream", leading his biographer to speculate that he had an obsession with the number.

Composer Maury Yeston adapted Fellini's 8 1/2 for Broadway as the musical Nine, which won several Tony Awards in 1982, and was successfully revived in 2003 starring Antonio Banderas.

9 is a full-length album by the heavy metal band Mercyful Fate, released in 1999. Fairport Convention also released an album with the number for a title.

9 number - In sports

• A batting lineup in baseball consists of nine players.
• In chess, the maximum number of queens one side could possibly have after queening all pawns.
• Nine ball is the standard professional pocket billiards variant played in the United States.
• In rugby union the scrum-half wears the 9 shirt.
• In baseball, nine represents the right fielder's position.
• The retired uniform numbers of former baseball players Ted Williams, Roger Maris, and former hockey players Gordie Howe and Maurice Richard.

9 number - In technology

• ISO 9 is the ISO's standard for the transliteration of Cyrillic characters into Latin characters
• In the Rich Text Format specification, 9 is the language code for the English language. All codes for regional variants of English are congruent to 9 mod 256.
• On most phones, the 9 key is associated with the letters W, X, and Y (and sometimes also Z), but on the BlackBerry it is the key for M.
• In Mac OS X, the F9 function key tiles all open windows and sizes them to fit together.

9 number - In other fields

• Nine is the highest single-digit number in the decimal system.
• In the NATO phonetic alphabet, the digit 9 is called "niner".
• Nine is the number of musicians in a nonet.
• Nine babies born into a single birth are called nonuplets, although not one baby born into a set of nonuplets has ever survived infancy.
• A novena lasts for nine days.
• Nine judges sit on the United States Supreme Court.
• There are nine members of The Fellowship of the Ring in The Lord of the Rings saga, to balance and combat the nine Nazgûl, or Ringwraiths.
• The ordinal adjective is nonary.

• In Greek mythology there are nine Muses.
• In Egyptian mythology, there are nine major gods and goddesses (see also Ennead).
• There are nine basic personality types represented on the enneagram.
• In astrology, Sagittarius is the 9th astrological sign of the Zodiac.
• Joel Garreau identified nine different "nations" of North America.
• Nine months is approximately the gestation period for humans.
• A standard work day of 9 to 5 begins at 9 a.m.
• Stanines are measured on a scale of 1 to 9.
• The name of the area called Kowloon in Hong Kong literally means: nine dragons.
• Someone dressed "to the nines" is dressed up as much as they can be.

• Nine Lives Cat Food got its name from the legend that a cat has nine lives.
• Nine rank system
• The Nine Chapters on the Mathematical Art
• Nine Worthies

• 9: The Last Resort was a 1995 computer game.

• Historical years: 9 A.D., 9 B.C., or 1909

Category: Integers

Adapted from the Wikipedia article "9 number", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki