Literal atheism means not believing in a god or gods. Buddhists are atheists, but there are some atheists state that atheists must be exactly like them and not get involved in spirituality at all.....it's best not to confine atheism to such a level.
But if we walk in the light, as He is in the light, we have fellowship with one another, and the blood of Jesus, His Son, purifies us from all sin.