Jan Koum (Ukrainian: Ян Кум; born Yan Borysovych Kum, Ukrainian: Ян Борисович Кум, on February 24, 1976) is a Ukrainian-American billionaire businessman and computer programmer . He is the co-founder and former CEO of WhatsApp, a mobile messaging app which was acquired by Facebook in 2014 for US$19.3 billion. According to Forbes, he has an estimated net worth of US$13.8 billion as of September 2022, making him one of the richest people in the world. He entered the Forbes list of the 400 richest Americans in 2014 at No. 62, with an estimated net worth of $7.5 billion, the highest-ranked newcomer to the list that year. Koum was born in Kyiv, then in the Ukrainian SSR, on February 24, 1976. He grew up in Fastiv. In 1992, at the age of 16, he moved with his mother and grandmother to Mountain View, California. A social support program helped the family get a small two-bedroom apartment there. His father had intended to join the family later, but he never left Ukraine and died in 1997. Koum and his mother remained in touch with his father until his death. At first, his mother worked as a babysitter while he worked as a cleaner at a grocery store. His mother died in 2000 after a long battle with cancer.