You said it correctly, you can have as many stakeholders as you want on a project. In fact, public projects in a country have the whole population of a country as stakeholders. However, these stakeholders have very little influence over the project.
In any case, regardless of the actual number of stakeholders on a project, there is only a few stakeholders that have an actual saying in the project. The smaller the size of the project is, the smaller the number of "real" stakeholders on the project (really small projects can have 1 or two stakeholders).
Larger projects tend to have more stakeholders than smaller ones (this is a fact), but the number of real stakeholders (those who care about the project AND have a saying on the project - e.g. the stakeholders that you should care about) is never more than 10.