[Hussell]

The maximum IQ score anyone can get depends on the total number of people who have taken IQ tests so far. Even if every single person alive today took an IQ test (which is absurd in itself), the maximum IQ achievable would be between 190-197. In practice, I'd guess the maximum is somewhere between 170 and 185 (millions to tens of millions of IQ test results which were recorded).

Even then, you need special tests to distinguish between anyone with IQ higher than about 160 - all those people get the same (perfect) score on regular IQ tests.

So: claiming to have an IQ of 276? Bullshit. The guy whose parents claimed he scored 210 on an IQ test? Also bullshit. To get 210, there would have to have been ~500 billion IQ test results recorded.