Seven is the fourthsmallest prime number; the next is eleven. Seven is a Mersenne prime. This is because 2^{3}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 sixdigit repeating sequences in their decimal expansions. 1/7=0.142857142...
A sevensided polygon is a heptagon[?]. The regular ngons for n ≤ 6 can be constructed by ruler and compass alone, but the regular heptagon cannot.
The British fiftypence coin is a heptagon, with the sides curved to give it a constant radius.
Cities constructed amidst seven hills include:
Seven is also:
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