You could for example take A to be the set of all natural numbers whose decimal expression has a 0 in all the even-numbered places (counting from the right), and B to be the set of all natural numbers whose decimal expression has a 0 in all the odd-numbered places.

So for example the number n = 31416265 can be written 1010205 + 30406060 (with the first of those numbers being in A and the second one being in B).