# period of a prime

Let *p* be a prime. The period of the decimal expansion
of 1/*p* is often called **the period of p**.
This period always divides

*p*-1 and usually found by calculating the order of 10 modulo

*p*(which equals the period). If the period equals

*p*-1, then it is a

**full period prime**.

p | period | p | period | p | period | p | period | p | period | p | period |
---|---|---|---|---|---|---|---|---|---|---|---|

2 | * | 3 | 1 | 5 | * | 7 | 6 | 11 | 2 | 13 | 6 |

17 | 16 | 19 | 18 | 23 | 22 | 29 | 28 | 31 | 15 | 37 | 3 |

41 | 5 | 43 | 21 | 47 | 46 | 53 | 13 | 59 | 58 | 61 | 60 |

67 | 33 | 71 | 35 | 73 | 8 | 79 | 13 | 83 | 41 | 89 | 44 |

97 | 96 | 101 | 4 | 103 | 34 | 107 | 53 | 109 | 108 | 113 | 112 |

127 | 42 | 131 | 130 | 137 | 8 | 139 | 46 | 149 | 148 | 151 | 75 |

157 | 78 | 163 | 81 | 167 | 166 | 173 | 43 | 179 | 178 | 181 | 180 |

191 | 95 | 193 | 192 | 197 | 98 | 199 | 99 | 211 | 30 | 223 | 222 |

227 | 113 | 229 | 228 | 233 | 232 | 239 | 7 | 241 | 30 | 251 | 50 |

257 | 256 | 263 | 262 | 269 | 268 | 271 | 5 | 277 | 69 | 281 | 28 |

**See Also:** UniquePrime

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