Ira Curry, of Stone Mountain, says she bought just one ticket at Gateway Newsstand in Buckhead, a financial center of Atlanta.
Curry was driving to work Wednesday when a radio announcer talked about the Mega Ball being No. 7. Curry knew that was her Mega Ball number, so she called her daughter to check the ticket.
"Between joyful tears and laughter on the daughter's part, she relayed to her mother that her mother had won the lottery," said Alford.
Curry says she used family birthdays and lucky No. 7 to choose her numbers.
According to Georgia Lottery chief executive Debbie Alford, Curry chose to collect a lump sum of $123 million after taxes,
Young Soo Lee owns the store that sold Curry the winning ticket with her husband, Young Lee.
"I'm so excited and so happy now," said Young Soo Lee. "I love my store and the customer."
Despite earlier media reports, Young Soo Lee and her husband will not receive a bonus for selling the winning ticket.
The other winning ticket was sold at Jennifer's Gift Shop in San Jose, Calif. So far, that person has not come forward. The California store owner, identified as Thuy Nguyen, will receive $1 million, according to the state's lottery officials.
The $636 million Mega Millions jackpot is the second-largest in U.S. history.
The winning numbers on Tuesday night were: 8, 14, 17, 20, 39; Mega Ball: 7.
For a brief moment, there was some confusion over the outcome of Tuesday night's drawing.
The Mega Millions website actually showed there was no winner for a few minutes and indicated the jackpot for Friday would be $950 million. The mistake was corrected quickly.
Mega Millions changed its rules in October to help increase the jackpots by lowering the odds of winning the top prize. That means the chances of winning the jackpot are now about 1 in 259 million.
No ticket matched the six numbers needed to win last Friday's $425 million prize.
The largest Mega Millions jackpot was set in March 2012 at $656 million and was split by three winning tickets in Maryland, Illinois and Kansas.
The Associated Press contributed to this report.