At the moment you just only need 277 bitcoins to be a USD millionaire, but it depends on where do you live, for example in my country with only just 15 bitcoins you can be a millionaire and have a very very rich living.
By the way, i think holding 100 bitcoins will make everyone millionaire in a few years, it depends on the price, but i really believe in bitcoin for the future
i think in present time i have less than 5 bitcoins and now it may be easy to count to that much bitcoin do i need to become millionaire, i will never count that limit because i think it is not so easy to become a millionaire i think we need to work hard for it and only then it may be possible otherwise it may not be so easy.