von Neumann's up there too.

Other mathematicians were stunned by von Neumann's ability to instantaneously perform complex operations in his head. As a six-year-old, he could divide two eight-digit numbers in his head. When he was sent at the age of 15 to study advanced calculus under analyst Gábor Szegő, Szegő was so astounded with the boy's talent in mathematics that he was brought to tears on their first meeting.

Edward Teller admitted that he "never could keep up with him". Teller also said "von Neumann would carry on a conversation with my 3-year-old son, and the two of them would talk as equals, and I sometimes wondered if he used the same principle when he talked to the rest of us."

*Von Neumann was also noted for his eidetic memory (sometimes called photographic memory). Herman Goldstine wrote:

"One of his remarkable abilities was his power of absolute recall. As far as I could tell, von Neumann was able on once reading a book or article to quote it back verbatim; moreover, he could do it years later without hesitation. He could also translate it at no diminution in speed from its original language into English. On one occasion I tested his ability by asking him to tell me how A Tale of Two Cities started. Whereupon, without any pause, he immediately began to recite the first chapter and continued until asked to stop after about ten or fifteen minutes."