Seven

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...

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.

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

Cities constructed amidst seven hills include:

• Rome
• Cincinnati
• Pretoria

Seven is also:

• viewed as a lucky number in many Western cultures, and in Japanese culture.
• The number of days in a week.
• Seven Pillars of Wisdom is a book written by T. E. Lawrence.
• Seven is referred to in bingo as 'Lucky Seven'.
• The Seven Deadly Sins may be described as lust, avarice, envy, pride, sloth, gluttony and anger.
• Seven (or Se7en) is a 1995 film directed by David Fincher and starring Morgan Freeman, Brad Pitt and Kevin Spacey.
• Seven Sisters is an area in London.
• Seven Sisters is also a 1998 song album by pop singer Meja.
• Seven is considered the usual number for a witches' coven.
• There is a crewmember, Seven of Nine, in the Star Trek universe.
• The neutral pH level.
• The number of palms in an Egyptian Sacred Cubit.
• The number of musicians in a septet[?].
• William Shakespeare divided life into the Seven ages of man.
• The name of one of the monsters in the cartoon television show Seven Little Monsters.
• Seven is figurative number of seas.
• There are seven candles in the Jewish menorah.