I'd be scared to "retire" even at 65 if I only had $2m USD, but it's one of those things where you just have to take that risk. Or keep working.
Edit: I read about a couple that retired early 15 years ago on $800K, but they kept it all pretty much in investments and only liquidated what they needed. Now 15 years later, they have $1.2M left.

Fantastic, they must be prudent investors. I guess it all boils down to need vs greed, if you are happy and content with what you have, you should be able to retire on a relatively low corpus.