Oh you're talking about hotel rooms. Never mind what I just said :) I would say two-oh-oh-01

Two thousand and one. English is weird in the way we say our numbers. If you were saying 1901 - you would say nineteen-oh-one but for some reason when we're talking about the first decade of the of the 21st century we say thousand. If you have to say 1900 - you would say nineteen hundred. At least it's like that in Australia, I can't speak for the rest of the world. You will sound far more fluent if you use that. Hope this was helpful, Sara X

I would read that as two thousand one or twenty oh one as you put it.