A woman fills out a Mega Millions lottery ticket on October 19, 2018 in New York City. The Mega Millions jackpot is currently up to $970 million.

Although the jackpot keeps increasing, the odds of winning remain at one in 302.5 million. Tickets for Friday's drawing can be purchased until 10:45 p.m. ET, 15 minutes before the live televised drawing. Tickets cost $2 each.

The $1 billion prize refers to the annuity option. Most winners opt for cash, which for Friday night's drawing would be $565 million. A Mega Millions prize of any amount can be claimed up to one year from the date of the drawing.

The Mega Millions jackpot reached $1 billion on Friday, marking the second-largest prize in U.S. lottery history.

The prize has grown so large because no one has hit the jackpot since July 24, when a group in California won $543 million.

In 2016, Powerball had a $1.586 billion prize. The previous record jackpot in Mega Millions was a $656 million prize that was shared by winners from Kansas, Illinois and Maryland in March 2012.

If no one picks all six numbers in Friday night's drawing, the prize for Tuesday night's drawing would be $1.6 billion, tying the largest U.S. lottery prize.

The next Powerball drawing is at 10:59 p.m. ET Saturday.

--The Associated Press contributed to this report