MySQL regular expression to match a imploded item

Hello

I need to use MySQL's REGEXP (POSIX compliant) to search registries where
one field is an imploded set of integer values separated with pipes "|".
I need to match one of these imploded values directly on a sql select.
$sql = "SELECT FROM table WHERE imploded REGEX "????" . $number . "????";

Example, with the string "10|3|605|40" I need to match 605 but not 5, match
40 but not 4.
I'm not expert in regular expressions and I can't find the proper one.

Any help?

Thanks in advance
- David Strencsev