257 (number)

257 (two hundred [and] fifty-seven) is the natural number following 256 and preceding 258.

In mathematics[]

257 is a prime number of the form ${\displaystyle 2^{2^{n}}+1,}$ specifically with n = 3, and therefore a Fermat prime. Thus a regular polygon with 257 sides is constructible with compass and unmarked straightedge. It is currently the second largest known Fermat prime.^[1]

It is also a balanced prime,^[2] an irregular prime,^[3] a prime that is one more than a square,^[4] and a Jacobsthal–Lucas number.^[5]

There are exactly 257 combinatorially distinct convex polyhedra with eight vertices (or polyhedral graphs with eight nodes).^[6]

In other fields[]

• The years 257 and 257 BC
• 257 is the country calling code for Burundi. See List of country calling codes.
• .257 Roberts, rifle cartridge
• There is a Pac-Man themed restaurant called Level 257 located in Schaumburg, Illinois. It is in reference to the kill screen reached in Level 256 in the Pac-Man arcade game.
• 257ers is a German hip hop duo

References[]