How do you manage to have 100+ headmates?

Please don't take this question as an insult. I am genuinely curious. I don't know so many people in the real world, and I know about 10 of them closely. So I can imagine how there can be for example 10 headmates (I have 2 of them by the way). But how can you have 100 and more and still know the name and character of each? Such a situation blows my mind.