Integers with leading zeroes

[Laura Creighton]

The biggest use I have for decimal numbers that begin with 0 is in
credit card numbers, account numbers and the like where the first
check you do is 'does this thing have the correct number of digits'.
So far, all the examples I've been able to find in my code -- which
does this sort of stuff a lot -- is looking at string versions of
decimal numbers, but I suspect there is old code out there in the
wild which just used integers.

Laura