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7 ('''seven''') is the [http://en.wikipedia.org/wiki/Natural_number natural number] following 6  and preceding 8.

7 ('''seven''') is the [https://en.wikipedia.org/wiki/Natural_number natural number] following 6  and preceding 8.

==In mathematics==

==In mathematics==

* Seven is the fourth [http://en.wikipedia.org/wiki/Prime_number prime number]. It is not only a [http://en.wikipedia.org/wiki/Mersenne_prime Mersenne prime] (since 23 − 1 = 7) but also a [http://en.wikipedia.org/wiki/Double_Mersenne_prime double Mersenne prime] since it is itself the exponent for another Mersenne prime (127). It is also a [http://en.wikipedia.org/wiki/Newman-Shanks-Williams_prime Newman-Shanks-Williams prime], a [http://en.wikipedia.org/wiki/Woodall_prime Woodall prime], a [http://en.wikipedia.org/wiki/Factorial_prime factorial prime], a [http://en.wikipedia.org/wiki/Lucky_prime lucky prime], a [http://en.wikipedia.org/wiki/Happy_number happy number], a [http://en.wikipedia.org/wiki/Safe_prime safe prime] and the fourth [http://en.wikipedia.org/wiki/Heegner_number Heegner number].

* Seven is the fourth [https://en.wikipedia.org/wiki/Prime_number prime number]. It is not only a [https://en.wikipedia.org/wiki/Mersenne_prime Mersenne prime] (since 23 − 1 = 7) but also a [https://en.wikipedia.org/wiki/Double_Mersenne_prime double Mersenne prime] since it is itself the exponent for another Mersenne prime (127). It is also a [https://en.wikipedia.org/wiki/Newman-Shanks-Williams_prime Newman-Shanks-Williams prime], a [https://en.wikipedia.org/wiki/Woodall_prime Woodall prime], a [https://en.wikipedia.org/wiki/Factorial_prime factorial prime], a [https://en.wikipedia.org/wiki/Lucky_prime lucky prime], a [https://en.wikipedia.org/wiki/Happy_number happy number], a [https://en.wikipedia.org/wiki/Safe_prime safe prime] and the fourth [https://en.wikipedia.org/wiki/Heegner_number Heegner number].

* Seven is the lowest number which cannot be represented as the sum of the squares of three integers.

* Seven is the lowest number which cannot be represented as the sum of the squares of three integers.

* Seven is the [http://en.wikipedia.org/wiki/Aliquot_sum aliquot sum] of one number, the [http://en.wikipedia.org/wiki/Cubic_number cubic number 8] and is the base of the 7-aliquot tree.

* Seven is the [https://en.wikipedia.org/wiki/Aliquot_sum aliquot sum] of one number, the [https://en.wikipedia.org/wiki/Cubic_number 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 [http://en.wikipedia.org/wiki/Nilpotent nilpotent endomorphisms] from Cn with the same [http://en.wikipedia.org/wiki/Minimal_polynomial minimal polynomial] and the same rank are similar."

* n = 7 is the first natural number for which the next statement does not hold: "Two [https://en.wikipedia.org/wiki/Nilpotent nilpotent endomorphisms] from Cn with the same [https://en.wikipedia.org/wiki/Minimal_polynomial minimal polynomial] and the same rank are similar."

* 7 is the only dimension, besides the familiar 3, in which a [http://en.wikipedia.org/wiki/Cross_product vector cross product] can be defined.

* 7 is the only dimension, besides the familiar 3, in which a [https://en.wikipedia.org/wiki/Cross_product 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.[1] For example, 1/7 = 0.142 857 142.... and 2/7 = 0.285 714 285...

* 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.[1] For example, 1/7 = 0.142 857 142.... and 2/7 = 0.285 714 285...

* A seven-sided shape is a [http://en.wikipedia.org/wiki/Heptagon 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 [http://en.wikipedia.org/wiki/Centered_hexagonal_number centered hexagonal number].

* A seven-sided shape is a [https://en.wikipedia.org/wiki/Heptagon 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 [https://en.wikipedia.org/wiki/Centered_hexagonal_number 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 frieze groups, the groups consisting of symmetries of the plane whose group of translations is isomorphic to the group of integers.

* Seven is the sum of any two opposite sides on a standard six-sided die. When rolling two standard six-sided dice, seven 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.

* Seven is the sum of any two opposite sides on a standard six-sided die. When rolling two standard six-sided dice, seven 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.

==Evolution of the Glyph==

==Evolution of the Glyph==

In the beginning, various [http://en.wikipedia.org/wiki/Hindu 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 [http://en.wikipedia.org/wiki/Europe 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.[http://en.wikipedia.org/wiki/Seven]

In the beginning, various [https://en.wikipedia.org/wiki/Hindu 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 [https://en.wikipedia.org/wiki/Europe 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.[https://en.wikipedia.org/wiki/Seven]

==Quote==

==Quote==

==See also==

==See also==

*'''''[[0:8 God the Sevenfold|God the Sevenfold]]'''''

*'''''[[0:8 God the Sevenfold|God the Sevenfold]]'''''

* [http://en.wikipedia.org/wiki/Septenary Septenary (numeral system)]

* [https://en.wikipedia.org/wiki/Septenary Septenary (numeral system)]

* [http://en.wikipedia.org/wiki/Septenary_(Theosophy) Septenary (Theosophy)]

* [https://en.wikipedia.org/wiki/Septenary_(Theosophy) Septenary (Theosophy)]

* [http://en.wikipedia.org/wiki/Seven_climes Seven climes]

* [https://en.wikipedia.org/wiki/Seven_climes Seven climes]

* [http://en.wikipedia.org/wiki/Year_Seven_(School) Year Seven (School)]

* [https://en.wikipedia.org/wiki/Year_Seven_(School) Year Seven (School)]

==References==

==References==

* Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group (1987): 70–71

* Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group (1987): 70–71

==External links==

==External links==

* [http://www.sevenmagazine.org/ Seventy-seven things you need to know about 07]

* [https://www.sevenmagazine.org/ Seventy-seven things you need to know about 07]

[[Category: Mathematics]]

[[Category: Mathematics]]

[[Category: Cosmology]]

[[Category: Cosmology]]