It depends. You mean the number of Doctor Who episodes, or number of stories? In the full series (classic and new), there's 784 episodes, and 224 stories. There's lots of stories that split into two or three episodes, and a few that have many more. "The Daleks' Master Plan" consists of 12 episodes and, although usually considered as 4 stories, the 14 episodes of Season 23 were broadcast under the single title "The Trial of a Time Lord".