If it’s a number, you should be able to count the the number of digits after the fact with some math.
You can see an example below. The only difference is that since you already have numbers, there shouldn’t be a need to convert to all 1’s to make it work. I’m not sure though if such a large number would calculate properly, so no guarantee that it would work. This is of course if you need a count after the data has been input and saved to the table. If you need it in a form, then @gvalero’s idea is probably better.