In the example you gave, you can get the digit you want doing something like this:
First, convert it to string, so you can get indexes:
var number = 1234
var nstr = str(number)
then, get the index you want (remember indexes start in 0), and convert it back to int:
var digit = int(nstr)
Then, do whatever you want with the digit:
That should print 3. I assume there are other ways. Is that what you wanted?