The short answer is it isn't; there are clearly millions of atheists. There is a theological thought that if there are all powerful gods, there wouldn't be any atheists, so the fact that there are is an argument against gods' existence.
It's impossible to say, but the simple answer is too many.
Proponents of agnostic atheism do not believe in any particular deity because they feel it is impossible to know whether such beings exist. Nihilists feel that there is no point to life. These are completely different world views.
Agnosticism is the belief that it is impossible to know whether God exists. Agnostics neither affirm nor deny the existence of a deity due to lack of evidence or the limitations of human knowledge. This stance contrasts with atheism, which denies the existence of God, and theism, which affirms belief in a deity.
Atheism is a noun.
Atheism is the belief that there is no god.
There are no prophets of atheism.
George H. Smith has written: 'Atheism, Ayn Rand, and other heresies' -- subject(s): Atheism, Philosophy, Religion and state 'The Wealth of Nations Part 1' 'Why Atheism?' -- subject(s): atheism 'Atheism' -- subject(s): atheism, Atheism, Controversial literature, Christianity
Without Knowledge (or knowing). Used by people who say that it is impossible to know if there is a God or not. Some one who is doubtful or noncommittal about something. Some one who believes that it is impossible to know whether there is a God. Some one who is skeptical about the existence of God but does not profess true atheism.
Atheism is not a religion. [S] [V] [o] Here you are, a complete sentence with atheism.
Atheism is the lack of belief in God.
"Atheism is not a religion."
Atheism was never established, as it is not a religion.