Now that we know which teams are headed to the NCAA tournament, you may have started thinking about which teams to pick in the NCAA March Madness Bracket Challenge. You might even be thinking really big. Like a perfect bracket.  

Yeah, don’t get your hopes up.

Jeffrey Bergen, a professor of mathematics at DePaul University, has been crunching numbers on the topic for years. And they don't look good. Bergen says that the chances of someone filling out a perfect bracket is 1 in 9,223,372,036,854,775,808. That's one in more than nine quintillion.

To put how large that number is into proper perspective, Bergen reports that if you were to begin filling out brackets now and stacked each of the 9 quintillion pieces of paper on top of each other, the stack would reach all the way to the sun and back...over 3,000 times by the time you finished.

Impossible, you say? Well, yes, because even if every person on the planet joined in to help you, it would still take more than 2,500 years for seven billion people to fill out those 9 quintillion brackets.

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Sure, you can shrink that number by factoring in your unparalleled knowledge of college basketball, or simply by playing the odds. Even with some of those elements in mind, though, Bergen estimates the chances of filling out a perfect bracket to be around 1 in 128 billion. (He gets that number picking the higher-seeded team to win.)

“There is a lot of assumption based in all of this,” he said. “Of all the possible brackets out there, the most likely one is for the higher-seeded team to win. Now, keep in mind, it is still highly unlikely that every higher-seeded team will win.”

Still, Bergen says, that's more likely to score you that perfect bracket than just random choice.

“It’s still a lot harder than winning the lottery," he said.

Arash Khatibi, a graduate advisor at the University of Illinois, worked with professors Sheldon H. Jacobson and Douglas M. King crunching similar numbers to Bergan’s. The difference? They developed the BracketOdds website to help basketball fans choose as wisely as possible, using computer algorithms and past performances to determine the best picks.

“So, actually the probability of generating the perfect bracket based on our model is something like two to the power of 53,” Khatibi said.

That’s 9,007,199,254,740,992 different brackets. And, that’s using more basketball knowledge than just guessing. 

Khatibi says that the toughest round to get through is the first. Selecting 32 winning teams is a lot more difficult than selecting two. In the past six years, the closest anyone got to filling out a perfect bracket was in 2014 and 2015 when someone selected the first 31 games correctly. Still, they didn't make in through the first round. 

RELATED: How do your past brackets stack up to the competition? 

Khatibi and the professors working on the BracketOdds website's best advice? Fill out the bracket from top to bottom. 

But, again, even with that advice, your chances are slim. How slim? Well, these are 10 things more likely to happen, according to Bergen, than filling out a perfect bracket:

1. Steph Curry making 414 consecutive free throws. (The NBA record is 97).

2. Tom Brady completing 96 consecutive passes (The NFL record for most completed passes in a row is 25).

3. A Major League Baseball hitter smashing a homer in 17 straight at-bats (The MLB record is four straight homers).

4. A professional pitcher striking out 31 batters in a row (The current MLB record is 10 in a row).

5. The Golden State Warriors — or any great team that wins 85 percent of its games, as the Warriors are doing this year — winning 268 consecutive regular-season games (The current NBA record is 33).

6. The Chicago Cubs — or any great team that wins 64 percent of its games, as the Cubs did in winning the World Series in 2016 — winning 97 regular-season games in a row (The current MLB record is 26 in a row).

7. A professional bowler rolling 85 consecutive strikes, the eqiuivalent of more than 12 straight perfect games (Pro bowlers roll strikes about 60 percent of the time).

8. A professional bowler converting a 7-10 split nine consecutive times (Pro bowlers convert one in about 1 in every 145 tries).

9.  A professional golfer sinking a hole in one on five straight par 3s (Pro golfers hit ace a hole once every 2,500 attempts).

10. A professional golfer making 13 putts in a row from 50 feet (They make about 3 percent of those putts).

The point is, Bergen says, don’t feel bad when your bracket eventually busts. You're not alone in that.