It seems that while the game is autosaving, you can get inifinite amount of new citizens. It works like this: after new turn, game starts to autosave, if you can recruit new citizen, open up the train new citizen screen and choose which citizen you want. You press train, but nothing happens. You can then spam the button as much as you can and get so many as you like. For example I got 99 administrators in one game. Now I chose generals and I have 1500 legions after the autosave finished.

However, doing this will likely crash the game in future.