As long as you shorten your string in a mathematical way you will loose data and so uniqueness. As the CRC is much shorter than the original string, it is possible to have several strings that will produce the same CRC.
CRC is typically used to verify that a string has not been changed. So each String has a fix CRC. But a CRC will fit to several strings.
It is IMHO not useful to create just unique numbers.

Situation changes as long as you strip down the redundant data. To do this you have to think about the content of the string. Maybe you have always "0" at multiple, defined positions? In this case you can just cut them out.

... but this is what I stated in an earlier posting.

Marc