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Seven (7) is the natural number following six and preceding eight.

Seven is the fourth-smallest prime number; the next is eleven. Seven is a Mersenne prime. This is because 23-1=7, and seven is a prime number.

7 goes into 999,999 exactly 142,857 times, so fractions with 7 in the denominator have six-digit repeating sequences in their decimal expansions. 1/7=0.142857142...

In binary code seven is 111; in ternary code seven is 21; in quaternary numeral system code seven is 13; in quinary seven is 12; in senary seven is 11; in septenary seven is 10; in octal code and all codes above (such as decimal and hexadecimal) seven is 7. In Roman numerals seven is VII.

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.

There are seven of musicians in a septet and seven babies born in a set of septuplets. The most famous set of septuplets are the McCaughey Septuplets, who was born in 1997.

The British fifty-pence coin is a heptagon, with the sides curved to give it a constant radius.

Cities constructed amidst seven hills include:

Stephen Covey wrote a book called The Seven Habits of Highly Successful People.

Seven is also:

and occurs in the names of:
See also: five, six, seven, eight, nine, integer, list of numbers.

This article is about the number. For the year AD 7, see 7.

Preceded by:
Integers Succeeded by: