47. JAN KOUM

$10.1

BILLION  SELF-MADE SCORE: ) SOURCE: WHATSAPP AGE: 43 RESIDENCE: ATHERTON, CA PHILANTHROPY SCORE: Koum and his mother came to the U.S. from Ukraine when he was 16, fleeing anti-Semitism. His mother became a babysitter; Koum swept floors at a grocery store to help pay the bills. After working for several years at Yahoo, he started mobile messaging app WhatsApp in 2009 with Brian Acton (No. 342). Facebook acquired it in 2014 for $22 billion in cash and stock. Flush with cash and free time after resigning as CEO of WhatsApp last year, Koum reportedly purchased a $100 million home in Malibu in August. His Instagram suggests that he is an avid collector of rare Porsches.