Depends on the level of the question - if you are a census worker and asked my religion I would reply, I am a Buddhist. But many may not. The ethical, moral view of many atheists are same as a Buddhist.
If you take the " supernatural " elements like rebirth, kamma, Nibbana out of the equation then many educated and humanist atheists will fall into the framework that Buddha laid down.
There is a movement roughly called Buddhism 2.0 ( not that I subscribe to it ). I am just a curious member of Secular Buddhism Forum. My sister who is an atheist one day after discussion with me found that without knowing she is a Secular Buddhist.
Yes I am a Buddhist who follows 8 precepts for short bursts and 5 precepts always. But most do not. However most good people follow Dhamma with or without knowing it. And as Buddha said Dhamma is the essence.