Peace,
It depends on how you interpret the word 'deity'. God is certainly a One as God says that in Quran.
This is the definition for atheist according to Longman
a?Ethe?Eist / e?cist / noun
someone who does not believe that God exists
If you believe a God created the Universe and all within the folds of it, then you are no atheist but theist, or more accurately monotheist if you follow the teachings of Quran.
On the other hand, since I pondered upon creation some years ago I consider it illogical and irrational to be an atheist due to the fact that quite some intelligence is required to create the complex universe in which we live. Even if the universe would be, as some atheists argue, eternal, a kind of "background intelligence" is needed. If the "Big Bang" reoccurs as some sort of phenomenon then still some intelligence is required to make all this mass assemble in harmonious measures.
God bless you