Contents • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Mathematics [ ] • Seven, the fourth, is not only a (since 2 3 − 1 = 7) but also a since the exponent, 3, is itself a Mersenne prime. It is also a, a, a, a, a (happy prime), a (the only Mersenne safe prime), and the fourth. • Seven is the lowest natural number that cannot be represented as the sum of the squares of three integers.

(See.) • Seven is the of one number, the and is the base of the 7-aliquot tree. • 7 is the only number D for which the equation 2 n − D = x 2 has more than two solutions for n and x natural. Windows 98 Plus Screensavers Download here.

In particular, the equation 2 n − 7 = x 2 is known as the. • 7 is the only dimension, besides the familiar 3, in which a vector can. • 7 is the lowest of a known, although there may exist as yet unknown exotic smooth structures on the 4-dimensional sphere. • divided by 7 is exactly. Therefore, when a with 7 in the is converted to a expansion, the result has the same six- repeating sequence after the decimal point, but the sequence can start with any of those six digits. For example, 1/7 = 0.157. And 2/7 = 0.214.

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 = 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.

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Another example, 5238 ÷ 7 = 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. The regular n-gons for n ≤ 6 can be constructed by alone, but the regular heptagon cannot.

Representing heptagons (including seven) are called. Seven is also a. • Seven is the first integer reciprocal () with infinitely repeating representation. • There are seven, the consisting of of the plane whose group of is to the group of. • There are seven fundamental types of. Graph of the probability distribution of the sum of 2 six-sided dice • When rolling two standard six-sided, seven has a 6 in (or 1 / 6) probability of being rolled (1–6, 6–1, 2–5, 5–2, 3–4, or 4–3), the greatest of any number.

• The are seven problems in that were stated by the in 2000. Currently, six of the problems remain. • 7 is the last digit of Basic calculations [ ] 1 2 3 4 5 6 7 8 9 10 15 25 50 100 1000 7 × x 7 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 1.1 6 1 0.875 0. 538461 0.5 0.4 6 x ÷ 7 0. 142857 1 2 3 4 5 6 7 8 9 10 7 x 7 49 2401 49 887 282475249 x 7 1 2187 5 2 4782969 1 5 10 15 20 25 30 40 50 60 70 80 90 100 110 120 130 140 150 200 250 500 1000 x 7 1 5 13 7 21 7 26 7 34 7 42 7 55 7 101 7 114 7 130 7 143 7 156 7 202 7 215 7 231 7 244 7 260 7 303 7 404 7 505 7 1313 7 2626 7 41104 7 564355 7 11333311 7 Evolution of the glyph [ ]. In the beginning, various wrote 7 more or less in one stroke as a curve that looks like an 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 more rectilinear. The eastern developed the character from a 6 lookalike into an uppercase V lookalike. 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 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 in writings that use a long upstroke in the glyph for 1.