Depending on its size and health there can be anywhere from 54 to 172 seeds per dandelion head. A single plant can produce 2000 individual seeds, each capable of becoming a plant itself.
Each seed is released from the seed ball with a tiny individual parachute that will carry it on the wind. This serves to ensure the dandelion is spread as far and wide as possible.
Thought of as a noxious weed the misunderstood dandelion is one the most valuable medicinal herbs on earth. See post What are Dandelions Good For? Absolutely Everything!