WhatsApp has reached 600, 000, 000 active users according to Jan Koum, founder of the mobile messenger. This means that WhatsApp has doubled its user base over the past year and gained an additional 100 million users since April 2014, when the company hit the 500 million user milestone. So obviously, the mobile messaging startup continues to stand strong after being swallowed by Facebook. More or less unchallenged, it is still the world’s number one messaging application.
You will find more statistics at Statista