5

This number is a prime.

Just showing those entries submitted by 'Green': (Click here to show all)

The largest prime that can be the number of diagonals of an n-sided polygon (a pentagon in this case). [Green]

There are only 5 known regular polygons that can be constructed with Euclidean methods (i.e., by an unmarked straightedge and compass) that have a prime number of sides. [Green]

There are 5 known repunit primes. [Green]

The total number of multidigit primes whose digits are consecutive digits. Can you find all 5? [Green]

'A' is the only letter in the English alphabet that contains 5 non-straight angles (three acute and two obtuse). [Green]