I watched this video, and it literally blew my mind away. It is about Daniel Paul Tammet. Here is an excerpt about Daniel :
Daniel Paul Tammet is a British high-functioning autistic savant gifted with a facility for mathematical calculations, sequence memory, and natural language learning. He was born with congenital childhood epilepsy. Experiencing numbers as colors or sensations is a well-documented form of synesthesia, but the detail and specificity of Tammet's mental imagery of numbers is unique. In his mind, he says, each number up to 10,000 has its own unique shape and feel, that he can "see" results of calculations as landscapes, and that he can "sense" whether a number is prime or composite. He has described his visual image of 289 as particularly ugly, 333 as particularly attractive, and pi as beautiful. Tammet not only verbally describes these visions, but also creates artwork, particularly watercolor paintings, such as his painting of Pi.