Koum is a co-founder and former chief executive of WhatsApp, a messaging app that has been downloaded onto more than six billion devices. The app was launched in 2009 and sold to Facebook, the world's largest social-networking company, for $22 billion in 2014. Koum was a Facebook director for 3.5 years before leaving in 2018.
The majority of Koum's fortune is derived from the proceeds he received after selling WhatsApp to the world's largest social-networking company for $22 billion in cash and stock in February 2014. He owned about 43% of the company at the time of the sale, according to a Bloomberg analysis of October 2014 SEC filings. The billionaire received more than 76 million shares of Facebook and almost $2 billion in cash in the transaction, according to an October 2014 filing with the US Securities and Exchange Commission.
WhatsApp has been downloaded onto more than six billion devices as of September 2021, according to data from app intelligence firm Sensor Tower cited in a Bloomberg article. Koum sold $8 billion worth of shares between 2015 and when he left the firm in 2018, according to a Bloomberg analysis of stock exchange filings. His remaining holding of about $2 billion in Facebook shares wasn't disclosed in subsequent filings and was assumed to have been sold in a May 31, 2019 update to this analysis.
Koum has spent more than $300 million on three residential properties near Los Angeles, California since 2019, according to February 2021 news reports. These are included here at cost prices.
Koum has also spent more than $300 million on two yachts and a support vessel since 2012, according to May 2023 news report. These are included at construction cost.
The value of his cash investments is based on an analysis of share sales, dividends, market performance, taxes and charitable contributions.
Koum was born and raised in a village outside of Kiev, Ukraine, the only child of a housewife and a construction manager. He immigrated to California with his mother at age 16, enrolling at San Jose State University and working at Ernst & Young as a security tester. He got a job as an infrastructure engineer at Yahoo in 1997, where he met his future business partner Brian Acton. Koum's father died the same year; his mother died three years later.
Koum left Yahoo in October 2007. He started mobile-messaging service WhatsApp on Feb. 24, 2009, his birthday. Six months later, Acton persuaded five former Yahoo colleagues to invest $250,000 in seed funding, and was granted co-founder status and a stake in the company. Sequoia Capital invested about $58 million in the startup in multiple stages.
Facebook, the world's largest social network, agreed to purchase WhatsApp in February 2014 for $22 billion in cash and stock, the biggest Internet acquisition in more than a decade. He announced he was leaving WhatsApp in an April 30, 2018 Facebook post.