(CNN) Lottery officials have this advice for the holder of the winning ticket from Tuesday night's $1.537 billion Mega Millions jackpot: Take a deep breath, then give us a call.

The winning numbers -- 5, 28, 62, 65 and 70, with a Mega Ball of 5 -- were sold at a KC Mart gas station and convenience store in upstate South Carolina outside Simpsonville, a city of about 18,000 near Greenville.

It's the largest US jackpot won by a single ticket, and it's the nation's second-largest jackpot ever, just short of a $1.586 billion Powerball prize split by three tickets in January 2016.

Now the big question is: Who won?

"Sign the back of that (ticket). Take a few days. Take that deep breath again. (Then) call the lottery," South Carolina Education Lottery Chief Operating Officer Tony Cooper said at a Wednesday news conference outside the store where the ticket was sold.