229 (number)

Template:Infobox number 229 (two hundred [and] twenty-nine) is the natural number following 228 and preceding 230.

In mathematicsEdit

It is the fiftieth prime number, and a regular prime.<ref>Template:Cite OEIS</ref> It is also a full reptend prime, meaning that the decimal expansion of the unit fraction 1/229 repeats periodically with as long a period as possible.<ref>Template:Cite OEIS</ref> With 227 it is the larger of a pair of twin primes,<ref>Template:Cite OEIS</ref> and it is also the start of a sequence of three consecutive squarefree numbers.<ref>Template:Cite OEIS</ref> It is the smallest prime that, when added to the reverse of its decimal representation, yields another prime: 229 + 922 = 1151.<ref>Template:Cite OEIS</ref>

There are 229 cyclic permutations of the numbers from 1 to 7 in which none of the numbers is mapped to its successor (mod 7),<ref>Template:Cite OEIS</ref> 229 rooted tree structures formed from nine carbon atoms,<ref>Template:Cite OEIS</ref> and 229 triangulations of a polygon formed by adding three vertices to each side of a triangle.<ref>Template:Cite OEIS</ref> There are also 229 different projective configurations of type (12₃12₃), in which twelve points and twelve lines meet with three lines through each of the points and three points on each of the lines,<ref>Template:Cite OEIS</ref> all of which may be realized by straight lines in the Euclidean plane.<ref>Template:Cite OEIS</ref><ref>Template:Citation.</ref>

The complete graph K₁₃ has 229 crossings in its straight-line drawing with the fewest possible crossings.<ref>Template:Cite OEIS</ref><ref>Template:Citation.</ref>