That's more than I'd have thought. When I quit my job in 2013 I just let the money sit there for 5 years until I learned more about investing and realized I'd lost a ton of money by having it gain a couple dollars a month.

Open an IRA if you don't have one, call your 401k administrator once you've quit and tell them you want to roll it into the IRA. Once it's in there, make sure you invest it, otherwise it's just sitting as cash and getting no interest. Look at the prime directive as to how you may want to invest but typically index funds are safest.