|Unicode representation of Roman numeral||Ⅶ, ⅶ|
|prefixes||hepta-/hept- (from Greek)|
For the 1995 American murder thriller movie, go to Se7en.
Seven is the fourth-smallest prime number; the next is 11. Seven is a Mersenne prime, since 23 - 1 = 7. Seven is also the fourth Mersenne prime exponent, the first Newman-Shanks-Williams prime, the third Lucas prime, and the first Woodall prime. 7 is also the second lucky prime, the second safe prime, and the fourth factorial prime. 7 is the smallest number that can't be represented as a sum of fewer than four nonzero squares. 7 is also a self number.
A seven-sided polygon is a heptagon. The regular n-gons for n ≤ 6 can be constructed by ruler and compass alone, but the regular heptagon cannot. Figurate numbers representing heptagons (including seven) are called heptagonal numbers. Seven is also a centered hexagonal number.
A group or a series of seven is a heptad.
7 is the only dimension, besides the familiar 3, in which a vector cross product can be defined.
In numeral systems
|over 7 (octal, decimal)||7|
The Arabic glyph
In the beginning, various Hindus wrote 7 more or less in one stroke as a curve that looks like an uppercase J upside down. The western Ghubar Arabs' main contribution was to make the longer line diagonal rather than straight, though they showed some tendencies to making the character more rectilinear. The eastern Arabs developed the character from a 6-look-alike into an uppercase V-look-alike. Both modern Arab forms influenced the European form, a two-stroke character consisting of a horizontal upper line joined at its right to a line going down to the bottom left corner, a line that is slightly curved in some font variants. As is the case with the European glyph, the Cham and Khmer glyph for 7 also evolved to look like their glyph for 1, though in a different way, and so they were also concerned with making their 7 more different. For the Khmer this often involved adding a horizontal line above the glyph. This is analogous to the horizontal stroke through the middle that is sometimes used in handwriting in the Western world but which is almost never used in computer fonts.
On the seven-segment displays of pocket calculators and digital watches, 7 is the number with the most common glyph variation (0 and 6 also have variant glyphs). Most calculators use three line segments, but on Sharp, Casio and a few other brands of calculators, 7 is written with four line segments.
- The atomic number of nitrogen.
- The number of periods, or horizontal rows of elements, on the periodic table.
- The number of carbon atoms in heptane, a hydrocarbon.
- The neutral pH - the pH level of pure water
- The number of objects in the solar system visible to the naked eye, the classical "planets" (Moon, Mars, Mercury, Jupiter, Venus, Saturn, Sun). A fact that is believed to have led to the concept of seven days of the week.
- Messier object M7, a magnitude 3.5 open cluster in the constellation Scorpius.
- The New General Catalogue object NGC 7, a 14th magnitude spiral galaxy in the constellation Sculptor
- The seven daughters of Atlas in the Pleiades (also called the "seven sisters").
- The Saros number of the solar eclipse series which began on -2590 April 8 and ended on -1310 May 16. The duration of Saros series 7 was 1280.1 years, and it contained 72 solar eclipses.
- The Saros number of the lunar eclipse series which began on -2595 July 15 and ended on -1008 February 22. The duration of Saros series 7 was 1586.6 years, and it contained 89 lunar eclipses.
In Cantonese, the 16th most popular language in the world, the number 7 is pronounced exactly like the word for the male genitalia. It is coined for the negative phrase "You are 7", which has a slightly different meaning to "You are the male genitalia". It is very popular among teens.
- The number of notes in the musical scale
- In music, the Roman numeral vii is the subtonic (bVII) or leading tone (VII) scale degree, chord, or diatonic function, when distinguished V = major and v = minor
There are several albums titled 7:
- A 2003 album by Enrique Iglesias: see 7 (Enrique Iglesias album).
- A 2000 album by S Club 7: see 7 (S Club 7 album)
- A 1997 album by Zap Mama: see 7 (Zap Mama album)
- A 1996 album by Apoptygma Berzerk: see 7 (Apoptygma Berzerk album)
- A 1992 album by James: see Seven (James album).
- A 1986 album by George Strait: see 7 (George Strait album)
- A 1985 album by David Meece: see 7 (David Meece album)
- A 1981 album by Madness: see 7 (Madness album)
- A 1991 album by Mannheim Steamroller: see Fresh Aire 7
- A highly symbolic number in the Hebrew Bible, being, for example, the day on which God rested in Genesis
- The number of ayat in surat al-Fatiha
- The number of heavens in Islamic tradition
- The number of the Deadly Sins: lust, avarice, envy, pride, sloth, gluttony and anger
- The seven terraces of Mount Purgatory (one per deadly sin)
- The number of sacraments in the Roman Catholic faith
- Considered the usual number for a witches' coven
- The number of palms in an Egyptian Sacred Cubit
- The number of heads of the beast of the book of Revelation, and of some other monsters, like the hydra
- The minor symbol number of yang from the Taoist yin-yang.
- In rugby union, the openside flanker
- In baseball, seven represents the left fielder's position
- Boomer Esiason's jersey number
- The code for international direct dial phone calls to Russia and Kazakhstan
- On most phones, the 7 key is associated with the letters P, R, and S (there are a few phones that also put Q on 7, such as Sony Ericson cell phones), but on the BlackBerry it is the key for C and V.
- The number of digits in an American telephone number, excluding the area code
- The number of individual segments in one digit on a digital clock or calculator seven-segment display screen
- In all Microsoft Office programs, the F7 function key calls up the spelling and grammar checker
- In most Sonic the Hedgehog video games, the number of Chaos Emeralds
- In ASCII character set, the bell character
- In an episode of Seinfeld, the name George Costanza desired to give his first-born (with Susan Ross) due to a promise he had made to the widow of Mickey Mantle, whose number was 7
- The name of one of the monsters in the cartoon television show Seven Little Monsters
- A character added to the cast of Married... with Children who was quickly removed.
In other fields
There are seven continents on Planet Earth.
Seven is the smallest positive integer requiring two syllables in English.
Serial sevens are used as a diagnostic test in medicine.
Seven is also:
- Seven is one of the two magazines along with Stella introduced by Sarah Sands of The Sunday Telegraph in the United Kingdom on November 62005.
- The maximum amount of times that you can fold a sheet of paper in half
- The largest number of sticks (or other cylindrical objects) that can be tied into a bundle such that the shape of the bundle remains fixed. This may have led to the number being viewed with mystical significance by ancient man.
- The number of spheres in the Ptolemaic system
- The name of musician/actor Andre Benjamin's and singer Erykah Badu's son, Seven.
- September was the seventh month in the ancient Roman calendar, as its name indicates. After the reform that led to the current order, the seventh month is July.
- In Astrology, Libra is the 7th astrological sign of the Zodiac.
- The traditional number of Wonders of the Ancient World.
- Viewed as a lucky number in many Western cultures, and in Japanese culture.
- The number of days in a week. Whether Saturday or Sunday is the seventh day varies across cultures.
- Septidi was the seventh day of the decade in the French Revolutionary Calendar
- Referred to in bingo as 'Lucky Seven'
- The number of the ages of man into which William Shakespeare divided a lifetime
- The figurative number of seas
- The number of colors of the rainbow (the asteroid 7 Iris is named after the rainbow goddess Iris)
- The number of basic principles of the bushido
- The number of points on a sheriff's star
- The average number of digits that can be stored in short-term memory
- The name of an elite agency of photojournalists founded by seven leading photographers, including James Nachtwey and others
- In the movie The Ring, the number of days until you die, after watching The Cursed Videotape.
- The title of:
- The stage name of musician Keith Volpone
- Part of the names of:
- Seven Pillars of Wisdom, a book written by T. E. Lawrence
- The Secret Seven, name of children adventure book by Enid Blyton
- The book Seven Years in Tibet
- Kurosawa's film The Seven Samurai, that inspired the 1960 movie with Steve McQueen The Magnificent Seven and its own sequels
- The video game Final Fantasy VII
- Several groupings called the Seven Sisters
- Seven Sisters, a 1998 song album by pop singer Meja
- The crewmember, Seven of Nine, in the Star Trek universe
- The World Sevens Series in Rugby Union, including the Hong Kong Sevens
- the sport itself
- The Seven Network of Australia
- The Seven Habits of Highly Effective People, a book by Stephen Covey
- The traditional count of Basque provinces as expressed in the slogan Zazpiak Bat
- In Galician folklore, the seventh son will be a werewolf. In other folklores, after six daughters, the seventh child is to be a son and a werewolf. In other European folklores, the seventh son of a seventh son will be a vampire.
- Sevens is a card game
- 007, codename for James Bond, a fictional secret spy agent
- When rolling two standard six-sided dice, you are statistically more likely to roll a seven than any other number
- In the Sailor Moon cartoon, the characters must find the seven Nijizuishou.
- Seven is the sum of any two opposite sides on a standard six-sided die
- In the Harry Potter series, seven is considered to be the most magically powerful number. Lord Voldemort is suspected to have split his soul into seven pieces.
- Many Bungie games directly and indirectly reference the number seven often. For example, the UESC Marathon from the self-titled game series was built by hollowing out Deimos, a moon discovered in 1877.
- In the Inuyasha series, the Shichinintai are, as their name says, a band of seven mercenaries.
- Historical years: A.D. 7, 7 B.C., or 1907