I have to admit I missed this one, but when I read it I was kind of surprised that President Obama's speechwriters/editors didn't catch it. During his inaugural address Obama said, "Forty-four Americans have now taken the presidential oath". Well, not quite.
Obama is the 44th President, but for reasons I've never fully understood Grover Cleveland was the 22nd and the 24th President because he served two non-consecutive terms. So only 43 Americans have taken the oath, although 44 Presidents have. Obviously, it's a technical thing, but any list of Presidents will include two listings for Cleveland. It's hardly an obscure fact.