Dragon vibrate very fast, so this explains why you have been misled to think that there are no small populations of dragons still living. My father has met one. I've met one. The one I've met's spirit lives in a vessel I made him. But, since you want technical numbers, there were once over 500,000 dragons alive, and that's a minimum number.
None. Dragons are mythical beasts.
Dragons live in many different areas.
A Gift of Dragons has 291 pages.
Dragons of Despair has 32 pages.
Dragons of Argonath has 416 pages.
The Dragons of Eden has 263 pages.
Up from Dragons has 418 pages.
The Dragons of Babel has 320 pages.
The Shadow Dragons has 432 pages.
Dragons in the Waters has 293 pages.
Dragons of War has 496 pages.
Here Be Dragons has 704 pages.