Breadcrumb: How many prophets *were* there?

One of Samuel's three signs to mark Saul's appointment as king is that Saul will meet a group of singing, music-making prophets, and that he will prophesy with them. In fact, this actually happens, to the amazement of Saul's acquaintances, to the point where "is Saul also among the prophets?" becomes a proverbial saying. But at this juncture we have to ask ourselves, how many prophets were there in ancient Israel? If there was an entire band of prophets travelling in a group, what was the point of having Samuel the prophet as leader? Were these just occasional prophets, or lesser prophets, or what? In either case, the waters are a little murky for Samuel, who pointed them out in the first place. (1 Sam. 10:5-6, 9-13)