Well, there's no fixed number. Some fantasy novels have as few as a couple of main characters and a few minor ones. But in grand, sprawling sagas, you could find upwards of 30 characters or even more, each playing a role in the richly woven narrative.
The number of characters in a fantasy novel can be quite diverse. It often depends on the scope and complexity of the story. A shorter or more focused tale might have around 5-10 significant characters, while an epic could have 20 or more.