The woman who's divorcing PayPal founder Elon Musk is getting $4.2 million in their divorce ... which is great ... until you remember he's reportedly worth $680 MILLION.

TMZ has obtained the divorce docs filed in L.A. County Superior Court, in which actressagreed to a settlement with her soon-to-be ex-husband ... whom she married in Sept. 2010 ... and then separated from in July 2011.