Ah, I’m stumped by this question. How on earth do you define the perfect number of people for a perfect party? More importantly is your number the same as my number or someone else’s number? I think this depends on what kind of party you have and where it is happening.
If you are having a family party, a getogether or a birthday party or a wedding or even an anniversary, then the right number is always going to be the number of family members you have! Plain and simple; if my family size (which will be nuclear family, uncle, aunts, cousins, nephews and nieces) is say around 70, then 70 is the perfect number for a family party. I tend to avoid most parties but if I do go for a family party, then I would want to see everyone there.
Now with friends it is a little more complicated. You have groups of friends, some of whom do not know each other. Like you could have friends from work and the previous companies that you have worked for and they won’t all know each other. What about your childhood school & college friends? They might not know each other. Now unless it’s a common theme party, like your birthday or engagement or wedding or a house warming party then everyone can come. Otherwise it’s always better if you can keep separate parties for groups.
Now this is just me and my opinion. I do not really enjoy large gatherings and avoid them as much as I can. I prefer smaller parties, groups of 5 to 10 and where everyone knows each other really well. Everyone can relax and put their feet up, drink a few, eat some good food and have a fun, relaxing time which is to unwind after the stress of the world. That is my kind of party.