New York Jets rookie quarterback Sam Darnold celebrates his 21st birthday on Tuesday, which means the soon-to-be-millionaire finally can legally go to a bar or casino. To honor the milestone, we've compiled 21 age-related factoids and memorable moments:

1. If Darnold cracks the starting lineup as a rookie, he'll be the youngest quarterback to start a game for the Jets. The mark is held by Joe Namath, who was 22 years, 118 days old when he made his starting debut on Sept. 26, 1965. Namath got his famous nickname -- Broadway Joe -- as a rookie. Is there a catchy moniker waiting for Darnold?

2. Would Darnold be the youngest QB in NFL history if he starts? No, but he would be really close. Tommy Maddox was 21 years, 81 days old when he made his first start for the Denver Broncos on Nov. 22, 1992. For the record, Darnold will be 21 years, 97 days old on Sept. 10, when the Jets open the season at the Detroit Lions.

3. This might not come as a shock, but Darnold is the youngest player on the current roster. In terms of Jets history, he could be the fourth-youngest to play in a game. The three youngest, according to Pro Football Reference: wide receiver Jalin Marshall (21 years, 52 days) in 2016, linebacker Marvin Jones (21 years, 69 days) in 1993 and defensive end Leonard Williams (21 years, 85 days) in 2015.

4. Darnold is a babe among babes. Of the 13 quarterbacks drafted in April, he's the youngest by four months. The second-youngest is former college rival Josh Rosen, who turned 21 on Feb. 10. It must be an L.A. thing.

5. Not only was Darnold an early entrant into the draft, but he was also an early entrant into ... well, life. He was born two weeks early (June 5, 1997), checking in at 8 pounds, 5 ounces at Mission Hospital in Mission Viejo, California, according to Bleacher Report. His father wanted to name him Buck, but he was overruled. Broadway Buck actually has a nice ring to it. If they had only known.

6. As a kid, Darnold participated in a lot of sports, including basketball, baseball, soccer and taekwondo. His parents, Mike and Chris, wanted him to enjoy the full sports experience instead of focusing on one. That might explain why Darnold didn't become a starting quarterback until late in his sophomore year at San Clemente High School. Because of a broken foot, he started only two games as a junior, which means he has played only three seasons as a starting quarterback: senior year at San Clemente and two years at USC. You might say he's a young 21, if that's possible.

7. His first high school start was the stuff of legend. With three minutes remaining in the game, Darnold rallied his team from a 21-7 deficit to win 29-21.

8. Darnold was only 2 when his grandfather died. Dick Hammer lived a storybook life: He was a basketball player at USC, a member of the 1964 U.S. Olympic volleyball team, an actor on TV (he played Captain Hammer in the series "Emergency!") and an original Marlboro Man in cigarette advertisements in the 1970s. He also served as a firefighter in the Los Angeles area. "He was a stud," Darnold once said of his grandfather.

9. Keeping up a family tradition, Darnold dabbled in volleyball. Well, there was that one time when he was 16. Despite having no competitive experience, he played in a Manhattan Beach doubles tournament with his older sister, Franki, who competed at the University of Rhode Island. Somehow, they managed to make the playoffs. Did someone say, "Sandbagger?"

10. Sam was raised by athletic parents. His father was an offensive lineman at the University of Redlands in California, and his mother played volleyball at Long Beach City College.

11. Living in Orange County, about an hour south of Los Angeles, Darnold rooted for the Dodgers, Lakers and USC. Eric Gagne, Kobe Bryant and Reggie Bush were among his favorite athletes.

12. Darnold narrowed his college choices to USC, Duke and Utah. If he had picked Duke, he would've played for David Cutcliffe, who coached Peyton and Eli Manning in college. Darnold could have been an adopted member of the Manning family, but he decided to stay close to home, even though the Trojans had already signed two highly-rated quarterbacks, Max Browne and Ricky Town. Darnold wasn't intimidated by the competition, and ultimately, he prevailed.

13. How cool is this? At USC, Darnold co-hosted his own weekly podcast, "Season of Sam." Joined by Yogi Roth, a former college player and Pac-12 analyst, Darnold shared with listeners his journey through the season. They had guests, too, including funny man and USC alumnus Will Ferrell.

14. Darnold was only 19 years old when he delivered his signature performance, beating Penn State in the Rose Bowl. Suddenly, an entire nation knew his name.

15. Darnold respects his elders, especially when they're NFL legends. In early March, he and fellow rookie quarterback Josh Allen visited Bill Parcells at his home in Jupiter, Florida. They're all represented by agent Jimmy Sexton, who arranged the meeting. For close to four hours, the draft hopefuls absorbed wisdom from Parcells.

Recalling the meeting, Parcells told ESPN, "I was impressed with them. They were highly respectful. They knew how to behave. They were inquisitive. They were both eager to hear what I had to say. Neither of them is ready to be a star -- and that's a good thing. They're both intent on being good football players. Whatever comes with that eventually comes with it, but they're not trying to precede it."

16. One funny anecdote from the Parcells summit: The Hall of Fame coach said he was taken aback when the quarterbacks told him they use elastic bands for their lower-body training. That's how Tom Brady does it, they told Parcells.

"Whoa, whoa, whoa," Parcells told Darnold and Allen. "Tom Brady is 40 years old. Tom Brady is in a preservation state. You're in a developmental state. You can't do the same things as him."

Parcells suggested leg squats, among other lifting techniques. Three weeks later, he texted both quarterbacks to see how they were doing as the draft approached. Darnold texted back immediately:

"Plenty of squats, coach. My legs are already stronger."

17. Speaking of Brady, he was between his freshman and sophomore years at Michigan when Darnold was born. Now they're AFC East rivals. Crazy.

18. The Jets' quarterbacks room includes the youngest player on the team and the oldest, Josh McCown, who turns 39 on July 4. McCown fired off this funny tweet after the draft:

Since posting texts is a thing now.... from my oldest daughter after we drafted Sam Darnold... pic.twitter.com/epu8QMkV0k

— Josh McCown (@JoshMcCown12) April 27, 2018

When the tweet was mentioned in a recent interview, McCown was asked if he could develop a father-son relationship with Darnold.

"More like an older big brother," he said with a smile. "Father-son is a little too close to home."

19. Does age matter for a quarterback? Let's go back to our conversation with Parcells. In 1993, age factored into his decision about whether to choose Drew Bledsoe or Rick Mirer with the No. 1 overall pick. Bledsoe was only 21 at the time of the draft; Mirer was 23. Ultimately, Parcells felt Bledsoe at 23 would be ahead of Mirer, and he was right -- good thing for the New England Patriots.

"Age is a number," Parcells said. "So much of it is getting to the right place with the right people to help you."

20. Darnold was 15 when he first posted on his Instagram account. His initial post? John Wooden's Pyramid of Success.

21. Now that he's 21, Darnold is old enough to drink legally. Cheers!