Next prime | 643 |

Previous prime | 631 |

Octal | (1201)_{8} |

Hexadecimal | (281)_{16} |

Prime gap | 2 |

29th Twin prime (the small number) | The big number is 643 . |

24th Prime triplet (the smallest number) | The others are 643 and 647 . |

57th Sexy prime (the small number) | The big number is 647 . |

55th Prime of the Form 4n+1 | 4^{2} + 25^{2} |

25th Euler prime number | |

28th Sophie Germain prime |