It's a continuum, and things very low on the intelligence continuum might not be referred to as intelligent in everyday usage. But many calculators are Turing complete and can thus clearly perform computations that I would consider intelligent. The basic algorithms used by simple calculators to perform arithmetic would be extremely low on the intelligent continuum.

Intelligence isn't a binary property. Is it really a problem to say that a calculator has some intelligence? That it's more intelligent than e.g. a rock?