7 ( seven ) is the natural number following 6 and preceding 8. It is the smallest positive integer to be spoken with two syllables when pronounced in English.
In mathematics
- Seven is the fourth prime number. It is not only a Mersenne prime (since 2 3 − 1 = 7) but also a double Mersenne prime since it is itself the exponent for another Mersenne prime (127). It is also a Newman-Shanks-Williams prime, a Woodall prime, a factorial prime, a lucky prime, a happy number and a safe prime.
- Seven is the only number less than 15 which cannot be represented as the sum of the squares of three integers.
- Seven is the aliquot sum of one number, the cubic number 8 and is the base of the 7-aliquot tree.
- n = 7 is the first natural number for which the next statement does not hold: "Two nilpotent endomorphisms from C n with the same minimal polynomial and the same rank are similar."
- 7 is the only dimension, besides the familiar 3, in which a vector cross product can be defined.
- 999,999 divided by 7 is exactly 142,857. Therefore, when a vulgar fraction with 7 in the denominator is converted to a decimal expansion, the result has the same six-digit repeating sequence after the decimal point, but the sequence can start with any of those six digits. For example, 1/7 = 0.142 857 142.... and 2/7 = 0.285 714 285...
- A seven-sided shape is a heptagon. The regular n -gons for n ≤ 6 can be constructed by compass and straightedge alone, but the regular heptagon cannot. Figurate numbers representing heptagons (including seven) are called heptagonal numbers. Seven is also a centered hexagonal number.
- There are seven frieze groups, the groups consisting of symmetries of the plane whose group of translations is isomorphic to the group of integers.
- There are seven fundamental types of catastrophes.
- When rolling two standard six-sided dice, it is the sum of any two opposite sides on a standard six-sided die. It has a 6 in 36 (or 1/6th) probability of being rolled (1–6, 6–1, 2–5, 5–2, 3–4, or 4–3), the greatest of any number.
In numeral systems
In quaternary, 7 is the smallest prime with a composite sum of digits.
In the English language, 7 is the only 2-syllable natural, positive 1-digit number
List of basic calculations
Evolution of the glyph
In the beginning, various Hindus wrote 7 more or less in one stroke as a curve that looks like an uppercase J vertically inverted. 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, 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. This horizontal stroke is, however, important to distinguish the glyph for seven from the glyph for one in writings that use a long upstroke in the glyph for one.
On the seven-segment displays of pocket calculators and digital watches, 7 is the number with the most common glyph variation (0, 6 and 9 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 because, in Japan and Korea, 7 is written as ① in the illustration to the right.
While the shape of the 7 character has an ascender in most modern typefaces, in typefaces with text figures the character usually has a descender, as, for example, in .
Some people, especially in Europe, Latin America, and New England, write 7 with a line in the middle ("
7"), sometimes with the top line crooked. The line through the middle is useful to clearly differentiate the character from the number one, as these can appear similar when written in certain styles of handwriting.In science
- Roy G. Biv = red, orange, yellow, green, blue, indigo, and violet were originally named as the seven colors of the rainbow, though blue and indigo are considered by some to be the same color.
- The number of spots on a common ladybug.
- The seven days of the week.
Biology
- With very few exceptions, all mammals' and birds' necks have seven bones.
- There are seven types of virus according to the Baltimore classification.
Chemistry
- A neutral pH value between acidity and alkalinity.
- The atomic number of nitrogen.
- The number of carbon atoms in heptane, a hydrocarbon.
- The number of periods, or horizontal rows of elements, on the periodic table.
Astronomy
- The number of stellar objects in the solar system visible to the naked eye from Earth— the Sun, the Moon and the five classical naked eye planets: Mars, Mercury, Jupiter, Venus, and Saturn.
- 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 number of daughters of Atlas in the Pleiades (also called the "seven sisters").
- The number of saints appearing in a constellation called "Saptharishi Mandalam" in Indian astronomy.
- The number of stars in the constellations of The Big Dipper and Orion.
- 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 1,280.1 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 1,586.6 years, and it contained 89 lunar eclipses.
- The Roman numeral VII stands for white dwarfs in the Yerkes spectral classification scheme.
- The Roman numeral VII (usually) stands for the seventh-discovered satellite of a planet or minor planet (e.g., Jupiter VII).
In technology
- The code for international direct dial phone calls to Russia and Kazakhstan.
- There are seven classes of plastics used in packaging applications.
- The resin identification code used in recycling to identify "other" plastics such as polycarbonate
- In Microsoft's Rich Text Format specification, seven and all numbers congruent to it modulo 256 refer to variants of the German language.
- System 7, a Macintosh operating system from the early 1990s
- Windows 7, an upcoming Microsoft operating system
- In the ASCII character set, the bell character.
- There are Seven Tools of Quality.
- There are seven layers in the OSI model.
- There are seven logic gates. NOT, AND, OR, NAND, XOR, NOR, XNOR
- The seven-segment display, is an electronic device that uses seven individual segments to create one digit; it is used in display devices like digital clocks and some basic calculator screens, amongst others.
In the classical world
In classical antiquity:
- Seven against Thebes
- Seven Emperors (and period; Rome, history)
- Julius Caesar, Augustus, Galba, Hadrian, Nerva, Sallust, Vespasian
- Seven hills of Rome
- Seven Liberal Arts
- Seven Sages
- Seven Wonders of the ancient world
Seven-Thunders by Russell Thomas ~ Home
Seven-Thunders is based on true events, dramatized and enhanced for inspirational and entertainment value.
Seven Thunders
Spiritual community combining the Christian contemplative tradition and the Zen Buddhist tradition of the Diamond Sangha. Offers regular meditation and group meditation retreats.
Welcome to Seven Thunders Ministry
Seven Thunders Ministry- A Mi'kmaq Native Healing/Deliverance and Teaching Ministry! Exciting teachings in Bible! Hebrew/Greek Word a Week, Prophet's Corner, Online Prayer ...
SevenThunders
SEVEN THUNDERS Then I saw another Mighty Angel coming down from heaven. He was robed in a cloud, with a rainbow above His head; His face was like the sun, and His legs were ...
Seven Thunders on MySpace Music - Free Streaming MP3s, Pictures ...
MySpace Music profile for Seven Thunders. Download Seven Thunders Bossa Nova / / music singles, watch music videos, listen to free streaming mp3s, & read Seven Thunders's blog.
Seven Thunders (1957)
Directed by Hugo Fregonese. With Stephen Boyd, James Robertson Justice, Kathleen Harrison. Escaping British prisoners of war hide out in German occupied France. Visit IMDb for ...
Seven Thunders-Sitting schedule
Sitting ‘Round Town. We are pleased to have Leonard Marcel Roshi and Br. Mark Filut OCSO lead our local sittings, giving talks and/or providing ...
THE SEVEN THUNDERS OF THE LIVING GOD - UNDER CONSTRUCTION
www.Constellation7.org/TheMazzarothMission . www.TheSevenThunders.org/Constellation-Seven UNDER CONSTRUCTION FOR THE LIVING GOD. www.Constellation7.org
Seven Thunders on MySpace Music - Free Streaming MP3s, Pictures ...
MySpace Music profile for Seven Thunders. Download Seven Thunders Progressive / Other / Experimental music singles, watch music videos, listen to free streaming mp3s, & read Seven ...
Theseventhunders
Adventist historical pionner teaching ... Welcome : Welcome to my web site of bible prophecy.This web site is a compilation seventh-day adventist historical pioneer teaching.