Numbers are abundantly found in Plato's works but it seems (to me at least) that 5 plays a rather important role. The platonic solids are five, of course, even if they come rather later, the Timaeus being considered as one of the last dialogues. Also In the Critias there are five pairs of male twins. In the Sophist "the five greatest kinds" are discussed; in the Philebus four classes are considered with Socrates making the provision
if I want a fifth at some future time you shall allow me to have it.
There are probably some more, but is there a resource listing all such instances? And are there some more or less academic (not fringe) comments/references about this specific number in Plato?