Getting valie between two fields? (mysql)

I have a table something like this: __________ | id | number |

| 1 |       1     |
| 2 |      23    |
| 3 |      59    |
| 4 |     103   |

If I have a number, say 30, I need to get the last number it's above - in this case id 2. Any ideas? -- The above message is encrypted with double rot13 encoding. Any unauthorized attempt to decrypt it will be prosecuted to the full extent of the law.