7
<templatestyles src="Module:Hatnote/styles.css"></templatestyles>
Lua error in package.lua at line 80: module 'strict' not found.
|
||||
---|---|---|---|---|
Cardinal | seven | |||
Ordinal | 7th (seventh) |
|||
Numeral system | septenary | |||
Factorization | prime | |||
Prime | 4th | |||
Divisors | 1, 7 | |||
Roman numeral | VII, vii | |||
Greek prefix | hepta-/hept- | |||
Latin prefix | septua- | |||
Binary | 1112 | |||
Ternary | 213 | |||
Quaternary | 134 | |||
Quinary | 125 | |||
Senary | 116 | |||
Octal | 78 | |||
Duodecimal | 712 | |||
Hexadecimal | 716 | |||
Vigesimal | 720 | |||
Base 36 | 736 | |||
Greek numeral | Z, ζ | |||
Amharic | ፯ | |||
Arabic, Kurdish, Persian | ٧ | |||
Sindhi, Urdu | ۷ | |||
Bengali | ৭ | |||
Chinese numeral | 七, 柒 | |||
Devanāgarī | ७ | |||
Telugu | ౭ | |||
Tamil | ௭ | |||
Hebrew | ז | |||
Khmer | ៧ | |||
Thai | ๗ | |||
Kannada | ೭ | |||
Malayalam | ൭ |
7 (seven) is the natural number following 6 and preceding 8. It is the only prime number preceding a cube.
The seven Classical planets resulted in seven being the number of days in a week.[citation needed] It is often considered lucky in Western culture and is often seen as highly symbolic. Unlike Western culture, in Vietnamese culture, the number seven is sometimes considered unlucky.[citation needed]
It is the first natural number whose pronunciation contains more than one syllable.
Contents
Evolution of the Arabic digit
In the beginning, Indians 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 digit more rectilinear. The eastern Arabs developed the digit from a form that looked something like our 6 to one that looked like an uppercase V. Both modern Arab forms influenced the European form, a two-stroke form consisting of a horizontal upper stroke joined at its right to a stroke going down to the bottom left corner, a line that is slightly curved in some font variants. As is the case with the European digit, the Cham and Khmer digit for 7 also evolved to look like their digit 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 to the top of the digit.[1] 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 writing that uses a long upstroke in the glyph for 1. In some Greek dialects of the early 12th century the longer line diagonal was drawn in a rather semicircular transverse line.
On the seven-segment displays of pocket calculators and digital watches, 7 is the digit with the most common graphic variation (1, 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, Korea and Taiwan 7 is written with a "hook" on the left, as ① in the following illustration.
While the shape of the character for the digit 7 has an ascender in most modern typefaces, in typefaces with text figures the character usually has a descender, as, for example, in .
Most people in Continental Europe,[2] and some in Britain and Ireland as well as Latin America, 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 digit from the digit one, as the two can appear similar when written in certain styles of handwriting. This form is used in official handwriting rules for primary school in Russia, Ukraine, Bulgaria, Poland, other Slavic countries,[3] France,[4] Italy, Belgium, Finland,[5] Romania, Germany, Greece,[6] and Hungary.[citation needed]
Mathematics
Seven, the fourth prime number, is not only a Mersenne prime (since 23 − 1 = 7) but also a double Mersenne prime since the exponent, 3, is itself a Mersenne prime.[7] It is also a Newman–Shanks–Williams prime,[8] a Woodall prime,[9] a factorial prime,[10] a lucky prime,[11] a happy number (happy prime),[12] a safe prime (the only Mersenne safe prime), a Leyland prime of the second kind and the fourth Heegner number.[13]
- Seven is the lowest natural number that cannot be represented as the sum of the squares of three integers. (See Lagrange's four-square theorem#Historical development.)
- Seven is the aliquot sum of one number, the cubic number 8 and is the base of the 7-aliquot tree.
- 7 is the only number D for which the equation 2n − D = x2 has more than two solutions for n and x natural. In particular, the equation 2n − 7 = x2 is known as the Ramanujan–Nagell equation.
- 7 is the only dimension, besides the familiar 3, in which a vector cross product can be defined.
- 7 is the lowest dimension of a known exotic sphere, although there may exist as yet unknown exotic smooth structures on the 4-dimensional sphere.
- 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.[14] For example, 1/7 = 0.142857 142857... and 2/7 = 0.285714 285714....
- In fact, if one sorts the digits in the number 142,857 in ascending order, 124578, it is possible to know from which of the digits the decimal part of the number is going to begin with. The remainder of dividing any number by 7 will give the position in the sequence 124578 that the decimal part of the resulting number will start. For example, 628 ÷ 7 = <templatestyles src="Sfrac/styles.css" />89+5/7; here 5 is the remainder, and would correspond to number 7 in the ranking of the ascending sequence. So in this case, 628 ÷ 7 = 89.714285. Another example, 5238 ÷ 7 = <templatestyles src="Sfrac/styles.css" />748+2/7, hence the remainder is 2, and this corresponds to number 2 in the sequence. In this case, 5238 ÷ 7 = 748.285714.
- A seven-sided shape is a heptagon.[15] The regular n-gons for n ≤ 6 can be constructed by compass and straightedge alone, but the regular heptagon cannot.[16] Figurate numbers representing heptagons (including seven) are called heptagonal numbers. Seven is also a centered hexagonal number.[17]
- There are seven frieze groups,[18] 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.[19]
- When rolling two standard six-sided dice, seven has a 6 in 62 (or <templatestyles src="Sfrac/styles.css" />1/6) probability of being rolled (1–6, 6–1, 2–5, 5–2, 3–4, or 4–3), the greatest of any number.[20] The opposite sides of a standard six-sided dice always add to 7.
- The Millennium Prize Problems are seven problems in mathematics that were stated by the Clay Mathematics Institute in 2000.[21] Currently, six of the problems remain unsolved.[22]
Basic calculations
Multiplication | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 15 | 25 | 50 | 100 | 1000 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
7 × x | 7 | 14 | 21 | 28 | 35 | 42 | 49 | 56 | 63 | 70 | 105 | 175 | 350 | 700 | 7000 |
Division | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
---|---|---|---|---|---|---|---|---|---|---|
11 | 12 | 13 | 14 | 15 | ||||||
7 ÷ x | 7 | 3.5 | 2.3 | 1.75 | 1.4 | 1.16 | 1 | 0.875 | 0.7 | 0.7 |
0.63 | 0.583 | 0.538461 | 0.5 | 0.46 | ||||||
x ÷ 7 | 0.142857 | 0.285714 | 0.428571 | 0.571428 | 0.714285 | 0.857142 | 1 | 1.142857 | 1.285714 | 1.428571 |
1.571428 | 1.714285 | 1.857142 | 2 | 2.142857 |
Exponentiation | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
---|---|---|---|---|---|---|---|---|---|---|
7x | 7 | 49 | 343 | 2401 | 16807 | 117649 | 823543 | 5764801 | 40353607 | 282475249 |
x7 | 1 | 128 | 2187 | 16384 | 78125 | 279936 | 823543 | 2097152 | 4782969 | 10000000 |
Radix | 1 | 5 | 10 | 15 | 20 | 25 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
110 | 120 | 130 | 140 | 150 | 200 | 250 | 500 | 1000 | 10000 | 100000 | 1000000 | |||
x7 | 1 | 5 | 137 | 217 | 267 | 347 | 427 | 557 | 1017 | 1147 | 1307 | 1437 | 1567 | 2027 |
2157 | 2317 | 2447 | 2607 | 3037 | 4047 | 5057 | 13137 | 26267 | 411047 | 5643557 | 113333117 |
In science
- Seven colors in a rainbow: ROYGBIV
- Seven Continents
- Seven Seas
- Seven climes
- The neutral pH balance
- Number of music notes in a scale
- Number of spots most commonly found on ladybugs
- Atomic number for Nitrogen
In Psychology
- Seven, plus or minus two as a model of working memory.
- Seven psychological types called the Seven Rays in the teachings of Alice A. Bailey
- In Western Culture, Seven is consistently listed as people's favorite number.[23][24]
- When guessing numbers 1-10 the number 7 is most likely to be picked.[25]
- Seven-year itch: happiness in marriage said to decline after 7 years
In culture
In literature
In sports
- Sports with seven players per side
- Seven is the least number of players a soccer team must have on the field in order for a match to start and continue.
- A touchdown plus an extra point is worth seven points.
See also
Wikimedia Commons has media related to [[commons:Lua error in Module:WikidataIB at line 506: attempt to index field 'wikibase' (a nil value).|Lua error in Module:WikidataIB at line 506: attempt to index field 'wikibase' (a nil value).]]. |
Look up seven in Wiktionary, the free dictionary. |
- Diatonic scale
- Lucky number
- Symbolism of the number 7
- Seven Wonders of the Ancient World
- Seven days of the Week
- Septenary (numeral system)
- Year Seven (School)
- Se7en (disambiguation)
- Sevens (disambiguation)
- One-seventh area triangle
- Z with stroke (Ƶ)
- List of highways numbered 7
Notes
- ↑ Georges Ifrah, The Universal History of Numbers: From Prehistory to the Invention of the Computer transl. David Bellos et al. London: The Harvill Press (1998): 395, Fig. 24.67
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ "Education writing numerals in grade 1." Archived 2008-10-02 at the Wayback Machine(Russian)
- ↑ "Example of teaching materials for pre-schoolers"(French)
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Bryan Bunch, The Kingdom of Infinite Number. New York: W. H. Freeman & Company (2000): 82
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
References
- Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group (1987): 70–71
- Webarchive template wayback links
- Articles with hatnote templates targeting a nonexistent page
- Articles to be merged from August 2021
- Articles with invalid date parameter in template
- Articles containing Urdu-language text
- Articles with unsourced statements from December 2021
- Articles with unsourced statements from September 2021
- Commons category link from Wikidata
- Integers
- 7 (number)