229 (number)

Short description: Natural number

| <- 228  | 229 |  230 ->

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← 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
Binary| 111001012
Ternary| 221113
Quaternary| 32114
Quinary| 14045
Senary| 10216
Octal| 3458
Duodecimal| 17112
Hexadecimal| E516
Vigesimal| B920
Base 36| 6D36

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]

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

## References

1. ↑ Sloane, N. J. A., ed. "Sequence A007703 (Regular primes)". OEIS Foundation. https://oeis.org/A007703.
2. ↑ Sloane, N. J. A., ed. "Sequence A001913 (Full reptend primes: primes with primitive root 10)". OEIS Foundation. https://oeis.org/A001913.
3. ↑ Sloane, N. J. A., ed. "Sequence A006512 (Greater of twin primes)". OEIS Foundation. https://oeis.org/A006512.
4. ↑ Sloane, N. J. A., ed. "Sequence A007675 (Numbers n such that n, n+1 and n+2 are squarefree)". OEIS Foundation. https://oeis.org/A007675.
5. ↑ Sloane, N. J. A., ed. "Sequence A061783 (Primes p such that p + (p reversed) is also a prime)". OEIS Foundation. https://oeis.org/A061783.
6. ↑ Sloane, N. J. A., ed. "Sequence A000757 (Number of cyclic permutations of [n with no i->i+1 (mod n))"]. OEIS Foundation. https://oeis.org/A000757.
7. ↑ Sloane, N. J. A., ed. "Sequence A000678 (Number of carbon (rooted) trees with n carbon atoms = unordered 4-tuples of ternary trees)". OEIS Foundation. https://oeis.org/A000678.
8. ↑ Sloane, N. J. A., ed. "Sequence A087809 (Number of triangulations (by Euclidean triangles) having 3+3n vertices of a triangle with each side subdivided by n additional points)". OEIS Foundation. https://oeis.org/A087809.
9. ↑ Sloane, N. J. A., ed. "Sequence A001403 (Number of combinatorial configurations of type (n_3))". OEIS Foundation. https://oeis.org/A001403.
10. ↑ Sloane, N. J. A., ed. "Sequence A099999 (Number of geometrical configurations of type (n_3))". OEIS Foundation. https://oeis.org/A099999.
11. ↑ Gropp, Harald (1997), "Configurations and their realization", Discrete Mathematics 174 (1–3): 137–151, doi:10.1016/S0012-365X(96)00327-5 .
12. ↑ Sloane, N. J. A., ed. "Sequence A014540 (Rectilinear crossing number of complete graph on n nodes)". OEIS Foundation. https://oeis.org/A014540.
13. ↑ 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 .

## See also

* Area code 229, assigned to Albany, Georgia, US
* List of highways numbered 229

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