26 May 2017


\(7\) is a prime number.

\(7\) is a Mersenne number, since it is prime and \(7=2^3-1\). It is also a double Mersenne number, since \(3\) is itself a Mersenne number (\(3=2^2-1\)).

\(7\) is the number of pieces of the Tangram.

\(7\) is the number of notes in the diatonic scale.

The heptagon is a polygon with \(7\) sides.

There are \(7\) days a week.

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