If we believe the proportion of atheists per country according to Wikipedia sources , dating from 2012-2014, China has the most atheists with nearly 846 million people, followed by India (40 million), Japan (39 million), the Philippines (21 million), Germany (14 million), Vietnam (12 million), France (12 million) and the United States (10 million).
We would reach a total of 1 billion and 118 million atheists worldwide. Knowing that this figure grows gradually but slowly. The proportion would be increased by up to 2% per year, at least in Western countries.
To these statistics, we should add all those who do not believe in god such as agnostics. They represent up to twice as many people in Western countries.