Paul Erdos
Paul ErdÅs (1913-1996) was a prominent 20th century mathematician. Homeschooled as a youth, he ultimately published more math papers (1500) than anyone and developed an elementary proof for some of the most challenging math problems, including the the Prime Number Theorem and Bertrand's conjecture that there was always at least one prime between n and 2n for n > 2.
Unlike many 20th century mathematicians, ErdÅs adhered to using elementary techniques rather than using newly developed fields of mathematics. ErdÅs also focused on solving existing problems rather than creating new ones.
Such is ErdÅs' acclaim among some mathematicians, that an 'ErdÅs number' is particularly prized, which is equal to the academic degrees of separation to ErdÅs. For example, the mathematician himself has a value of 0, mathematicians who coauthored a paper with him have a value of 1, those who coauthored a paper with them have a value of 2, and so on.