A 2005 survey published in Encyclopedia Britannica found that the non-religious made up about 11.9% of the world's population, and atheists about 2.3%. Using these figures that would mean about 161,000,000 people in the world are Atheists, while about 833,000,000 are non-religious.
It should be remembered that these figures are not reliable. In many parts of the world being openly atheist is not acceptable and prevents easy acceptance with the local society for business, friendship or political office. In in some cultures it is a death sentence. Atheists in many regions tend to keep their opinions to themselves and blend in with the local theist population.