The jackpot was the third-richest prize won with a single ticket in the history of lotteries in the United States.
The winners, who each chipped in $3 for the ticket, came into work Wednesday at the medical center in Garden Grove anyway, said Kaiser spokeswoman Barbara Shipnuck.
"They bought the entire staff lunch to celebrate," said Shipnuck. "For now, they all prefer to stay anonymous."
The ticket was bought at Rainbow Water, Juice, Flower & Gift, not far from Disneyland, where the owners will receive $1 million.
Owners Guadalupe and Jose Cordova, both 53, were considering selling the store a couple of years ago but changed their minds, said their daughter, Raquel Cordova.
"My mom's like, 'No, no, someday I'll hit it big and I'll be able to retire,"' Raquel Cordova said.
The couple, who immigrated to the United States from Mexico as teenagers, decided to take Wednesday off and let their kids work.
"Mom's gonna take a long vacation ... she's here seven days a week, even on Sundays," Raquel Cordova said.
For her part, Raquel is hoping that one of the big winners is a man who stopped by Tuesday to buy tickets, reports CBS News The Early Show national correspondent Hattie Kauffman.
"He bought a lot of tickets and said 'If I win, I'm going to buy you a Mercedes Benz,' so I'm waiting for him," she said.
Last month in Oregon, a family claimed the largest jackpot in U.S. lottery history won by a single ticket, $340 million. The numbers were drawn Oct. 19 in the other big multistate lottery, Powerball. Until then, the richest undivided lottery jackpot in U.S. history was the $314.9 million Powerball jackpot won by a West Virginia man on Christmas Day 2002.
In addition to California, Mega Millions is played in Georgia, Illinois, Maryland, Massachusetts, Michigan, New Jersey, New York, Ohio, Texas, Virginia and Washington.