229 (two hundred [and] twenty-nine) is the
natural number following
228 and preceding
230.
In mathematics
It is a
prime number, and a
regular prime.[1]
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.[2]
With
227 it is the larger of a pair of
twin primes,[3]
and it is also the start of a sequence of three consecutive
squarefree numbers.[4] It is the smallest prime that, when added to the reverse of its decimal representation, yields another prime: 229 + 922 = 1151.[5]
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),[6]
229
rooted tree structures formed from nine
carbon atoms,[7]
and 229
triangulations of a polygon formed by adding three vertices to each side of a triangle.[8]
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,[9] all of which may be realized by straight lines in the
Euclidean plane.[10][11]
^Aichholzer, Oswin; Krasser, Hannes (2007), "Abstract order type extension and new results on the rectilinear crossing number", Computational Geometry, 36 (1): 2–15,
doi:10.1016/j.comgeo.2005.07.005,
MR2264046.