229 (number)

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

← 228 229 230 →
← 220 221 222 223 224 225 226 227 228 229 → List of numbers Integers ← 0 100 200 300 400 500 600 700 800 900 →
Cardinal	two hundred twenty-nine
Ordinal	229th (two hundred twenty-ninth)
Factorization	prime
Prime	yes
Greek numeral	ΣΚΘ´
Roman numeral	CCXXIX, ccxxix
Binary	111001012
Ternary	221113
Senary	10216
Octal	3458
Duodecimal	17112
Hexadecimal	E516

In mathematics

It is the fiftieth 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]

The complete graph K₁₃ has 229 crossings in its straight-line drawing with the fewest possible crossings.^[12][13]