Singular values crop up in all kinds of contexts, BTW. Do ints support division? Well, yes, unless the denominator is zero.
I'm sorry. This is completely wrong. 0 is value -- a state of an numeric type -- just like singularity is the state of some iterators. In fact, I think you actually prove Chris' point, here; you've just extended the notion of singularity from iterators to integers. I would take that to mean that singularity is independent of type.
I should amend my previous statements. Maybe singularity is best viewed as a property of an expression. 0 is certainly a valid integral value. Unfortunately, there are no general named iterator values. What's a singular state for one may not be a singular state for another. I think an interesting question is, "what are the general properties of iterators that causes operations on them to result in singularity?". When is *i defined?