Who has an IQ of 400?

Answer 1

Sort of an interesting question, but such a person or organism has such a high IQ. Not even Einstein.
High IQ: Any score over 140 Genius IQ Score: 160 and up 180 and up - Profoundly gifted
There is information of a math genius named William James Sidis whose sister said the he had an IQ of about 300. But that has been mostly debunked. A researcher stating: "I have been researching the veracity of primary sources of various subjects for about twenty-eight years, and never before have I found a topic so satiated with lies, myths, half-truths, exaggerations, and other forms of misinformation as is in the history behind William Sidis".
He did attend Harvard at age 11. And did graduate but those students in his classes began to harass him physically. Sidis is cited as one of the possible inspirations for Matt Damon's character in Good Will Hunting.

Answer 2

It is not possible for someone to have an IQ of 400. The highest IQ ever recorded is around 228-230. IQ scores are standardized so that the average IQ is set at 100 with a standard deviation of 15.