Laszlo Andraschek's win went unnoticed until he made a donation to a hostel for the homeless this month, The Guardian reported.
He said buying the ticket was a last-minute decision at a railway station, when he was on his way to a workshop for recovering alcoholics.
"I had only picked six numbers and the female shop assistant reminded me that I needed to pick a seventh," he said. "I told her to make it 24 -- it doesn't matter anyway."
Andraschek, 55, now plans to use his winnings to establish a foundation to help addicts and abused women.
He said he first repaid his and his relatives' debts, bought a car, and bought apartments for his children.
Andraschek said he and his wife, Aniko, will not waste all their money.
"I have become rich but I have not become a different person. I could buy a large-screen TV because I can afford it, but I won't buy three because I can afford it," he said.