Converting string to integer, but preceding zero is being removed Follow up

This question has been answered so please close it... Thanks for the clarifications!!

I looked at the question above but there is an use case which we should consider before closing the issue:

I have a situation where I raise an order and the system generates a reference number as: 0000002443 I store that number as a string. When the system sends the order out, it sends two documents. One as a requisition with the above reference number and the other as a Purchase order with a reference: 0000002444

I need to be able to store the first reference number (i.e. 0000002443) as an Integer keeping the preceding zeroes and add +1 and store as a PO reference number (i.e.0000002444) to verify the orders later.

If I keep the first reference number as a String then I won't be able to add 1 to the reference number to get the PO reference Number.

It's a Follow up question: https://stackoverflow.com/questions/15025136/converting-string-to-integer-but-preceding-zero-is-being-removed