I was really unsure about tagging this question.
The misconception behind the OPs question lies in the area of order-theory (not every order has a well-defined concept of a "successor") and he was obviously (inference from the naiveness) referring to real-numbers or rational-numbers.
However, the original wording didn't realize that the question was regarding orders and the question asks about a particular property of a particular order The tag wiki features this:
Questions about properties of orders, general or particular, may fit into this category
But that leaves me a little inconclusive. Looking at the questions tagged with order-theory didn't shed any more light either. Is the question on-topic for order-theory?