Johanna Heundl, an Austrian immigrant who lives in the Los Angeles suburb of Covina, scooped the prize on Monday at Bally's casino.

I didn't realise I won the $22 million. I thought it was $22,000

Johanna Heundl

Shortly before breakfast, Ms Heundl had put just three one-dollar coins into the Megabucks machine - beating odds of more than 50 million to one with her win.

At first the retired printer did not realise just how big her windfall was, thinking that she had won $22,000.

"I looked away. When I looked back, the jackpot was there," Ms Heundl said,

"I didn't realise I won the $22 million. I thought it was $22,000," the astonished millionaire said.

Spending plans

In fact she had bagged a whopping $22,618,156.67 - the third biggest jackpot in the gambling city's history.

Now she is unsure what to do with the money.

"I just bought a new car. It's not even delivered yet," she said. "I have a house. I could remodel, or maybe buy a new house. I will go to Europe to see my family".

But nonetheless she was thrilled to win:

"I'm very happy it happened to me and I'm very grateful to everybody, I want to thank everybody, everybody's very nice," she said.

Enormous odds

The Megabucks machine is one of a large network that links a number of hotels in Las Vegas.

The company which makes the machines refused to disclose the odds of winning the jackpot - in which three megabucks symbols must appear - but acknowledged the odds against such a payout were "astronomical".

Experts estimate the odds are about 50 million to one - making it ten thousand times more likely you will be killed by a random falling object than you will win the megabucks.

The biggest jackpot of all time - worth $34.9m - was won in January 2000, and in 1998 one lucky player scooped $27.5m.