Today, English is the second or third most popular mother tongue in the world, with an estimated 350-400 million native speakers. But, crucially, it is also the common tongue for many non-English speakers the world over, and almost a quarter of the globe’s population - maybe 1½-2 billion people - can understand it and have at least some basic competence in its use, whether written or spoken.
It should be noted here that statistics on the numbers around the world who speak English are unreliable at best. It is notoriously difficult to define quite what is meant by “English speaker”, let alone the definitions of first language, second language, mother tongue, native speaker, etc. What level of competency counts? Does a thick creole (English-based, but completely incomprehensible to a native English speaker) count? Just to add to the confusion, there are at least 40 million people in the nominally English-speaking United States who do NOT speak English. In addition, the figures, of necessity, combine statistics from different sources, different dates, etc. You may well see large variations on any statistics quoted here.