Casting

Hi All,

Probably a very simple question, but... I am trying to cast a large number
approx
20 chars into text so I can manipulate it. I have tried

SELECT text(big_number) from table;

but this comes back in the format 3.2304234234233e+15 for example, whis is
no good. I essentially need the last four digits of the number (securing
credit card numbers is the idea), which I can only do by manipulating text
and casting it back.

Does anyone have any suggestions?

Many thanks,

Graham.