A Superhuman on '20/20' (VIDEO)

31-year old Daniel Tammet seems like a normal man. But beneath his unimposing exterior there lies an extraordinary human being.

Daniel is an autistic savant. Which basically means that he's amazingly gifted in certain areas, but has trouble recognizing his own gifts. Daniel also has synesthesia -- which means that he combines his senses in ways that most people cannot.

'20/20' (Tue., 10PM ET on ABC) examines Daniel as part of the show's "superhuman" series. During the course of the show, Daniel displays his incredible gifts in a shockingly offhand way. He is capable, for instance, of reciting the number "Pi" (an infinite number) from memory, without a mistake -- for five hours and nine minutes.

And even though Daniel already speaks eight languages fluently, he also manages to master the Icelandic language in a single week. Incredible! We are speechless. If you're not impressed, then maybe you should try learning a new language in seven days sometime -- it's hard, we promise you.