One has 9 questions, the other 6. They are not exactly the same but are very closely related.
So, should this be done? Right now, I've suggested "smooth-numbers" as tag synonym for "hamming-numbers", and if this comes through, I intend to go over the 6 of them and change the tag on these questions.
Is is the right course of action? If you support this, please vote at my tag synonym suggestion.