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Thanks YouTube EDU people.

This video featured in order:
Brady Haran (who makes Numberphile):
Derek Muller chose i -
Hank Green chose 2 -
Steve Spangler chose 13 -
Michael Stevens chose 17 -
Angela chose 7 -
Alex chose 27 -
Destin chose 21 -
Mike Rugnetta chose 1024 -
Caitlin chose 16 -
John Green chose 37 -
Henry Reich chose j -
Patrick chose 1729 -
CGPGrey chose 0 -
Vi Hart chose * -

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Brady: What's your favorite number and why?
Please leave a comment under this video so I can compare them all.
And in the mean time, here of the answers given by some of the top people of YouTube.
Now I had to interview some of these people in unusual locations like up trees and in toilets, so it's a bit of a hodge-podge, but it's also a bit of fun.

Derek: I'm Derek Muller of Veritasium, and My favorite number is i.

Hank: We're at the toilets at YouTube!

Derek: ...the square toot of negative one.

Hank: I'm Hank Green of SciShow and also CrashCourse and Vlogbrothers, and I'm a big fan of the number 2.

Steve: So my name is Steve Spangler.

Michael: I am Michael from the channel Vsauce.

Steve: I grew up in a family of professional magicians.

Michael: And my favorite number is the number 17 because I love making sevens with this little guy in the middle, so that you know it's not a one. It's something that my dad always did and I just adopted without ever thinking about it.

Steve: Number 13 has to be my absolute all time favorite number.

Angela: Hi! I'm Angela from YouTube EDU.

Steve: If you really want to see a real magician's magic wand, it's exactly thirteen inches long.

Angela: My number is seven and I know it's kind of generic, but when I was really young, people told me that it was a lucky number.

Michael: Seventeen was also the channel of Nickelodeon in Stilwell, Kansas, where I grew up.

Angela: So then I played a bunch of sports, and every single sport that I played, volleyball, tennis, whatever it was, my number was seven.

Brady: Michael from Vsauce has a little line, but you...

Angela: You know, I went through a phase where I definitely drew it with the line... and then I just decided: you know what, simpler is better.

Alex: I'm Alex from Bite Sci-zed, and my number is 27.

Angela: Every year, on 7-7, on July seventh, I do something special. So I started it on 7-7-7, and I remember I went kayaking that day, because I'd never been kayaking before.

Alex: As I was growing up, my favorite number was actually always my brother's age, but when I was 13 I decided that was silly, so the last one stuck. And so my favorite number has always stuck at 27.

Brady: Oh, you do one of those things.

Alex: I do, I do.

Brady: Why?

Alex: I don't know! I think it kind of distinguishes it. Sometimes my handwriting is terrible, and so my sevens look like ones, so I'll toss a little dash on it.

Michael: And seventeen is also significant for another reason... how come I can't remember it, it's prime, what was the other thing? This is called not respecting your favorite number well enough.  

Destin: I'm Destin, my number is 21. It's really hard to explain why.

Mike: My name is Mike Rugnetta from PBS Idea Channel, and my number is 1024.

Brady: Hang on, what's with that???

Mike: Zero fill. It's a compulsion, just from handwriting so many... My handwriting is really bad.

Caitlin: I'm Caitlin Hendrickson, work at YouTube, my number is sixteen.

John: Hi, I'm John Green of the Vlogbrothers, and my favorite number is 37, because it was the dorm room that I first lived in when I went to boarding school.

Caitlin: Growing up, I wanted to drive, so sixteen in the U.S. is when you can drive.

Brady (to Mike): Do you do that with your sevens?

Mike: I do, I do that with my sevens. And I do my ones like this, too.

Brady: Alright, 1024, why?

Mike: It's a very, sort of, nice round number in computing. Having a degree in computer science, it has a... magical quality about it, I guess.

Alex: So actually I also have a little bit of synesthesia, so numbers have colors for me, so 2 is green and 7 is yellow, so 27 is actually a very greenish yellow number.

Destin: You've heard of synesthesia. I don't have it, but I think it's amazing. But, to me there's certain sharpnessses for certain numbers.

Henry: My name's Henry, I make MinutePhysics videos, and my favorite number is j.

Michael: My first kiss wasn't until I was 18, so it was the last year that I lived, last full year I lived before I knew... what lips felt like.

Caitlin: And I always wanted to have a sweet 16 birthday party, which my parents never gave me...but I'll make up for that maybe, when I turn 30 in a couple of years.

Michael: Oh! Then the seventeenth floor is the floor that I lived on in New York, when I lived in Brooklyn. But I almost actually lived on the sixteenth floor, because the building skipped the thirteenth. Right, the elevators went right from 11 to 12 to 14, 15, 16, 17. Boom. He's been with me my whole life, basically.

Destin: So, certain numbers are sharper than others, so like a one would be kinda sharp, a two is very dull, but a 3 is very very high. They have this sharpness to them, I don't know what it is, and so it's like this. And if I take 3 and 7, and multiply them together, I get 21. And for some reason, 21 seems to be this very bright, cheerful, you know, proper number.

Brady: So how high will 21 be on the sharpness scale?

Destin: Oh, it's way up here. It's like off the page.

Patrick: Hi, I'm Patrick JMT and my favorite number, or one of my favorite numbers is 1729.

Henry: Now before you say "j isn't a number", I mean, j is a number.

CGP Grey: I'm CGP Grey, and my favorite number is zero. I like zero because it's not an obvious number, you can have counting systems where there's one thing, two things, three things, four things, but mathematics existed for a long time without having a zero as part of it. So it's a number, but it also isn't anything in and of itself.

Vi Hart: I'm Vi Hart, you have to tell me what a number is, if I'm gonna choose one. Alright. I'm having trouble with this.

Henry:  Similar to the way i is the square root of -1, but what that actually means is that i squared is -1, j squared is plus one. But j is not one.

CGP Grey: But one of the things that I like about zero is that it's the, kind of, unsung workhorse of the mathematical world. You have 0, and then if you want to make 10, you put a 1 in front of that zero. And now, we have ten things, and people focus on the 1, but it's really the 0 that is doing all the work to make that a ten. And then the same thing with 100 or 100,000, right, we keep adding zeros, we keep adding nothing, but making the numbers much much larger.

Vi Hart: Students in school are like, "Oh what's i, that's not really a number." And then there's j. j's a good one. It's already taken. 

Brady (to Henry): You know that Derek, you can see on there that Derek chose i. You chose j. What's the difference? Why'd you pick that one?

Henry: Who wants to pick the team that's going to win all the time? Who wants to pick the New York Yankees, you know, you wanna pick the underdog. You wanna pick the... you don't wanna pick what everyone else has already gone for.

Vi Hart: Star. Which... it's not a number. It's like a number. The thing is, it's smaller than all the positive numbers, and it's larger than all the negative numbers, but it's not zero. It gets confused with zero. This is one of those weird things you get in combinatorial game theory, and I like it. I think the very not-numberness of it... I think that's what appeals about a lot of these numbers to us, like the weirdness of j. The weirdness of i, the weirdness of zero.

CGP Grey: I like zero's non-obviousness and its incredible usefulness.

Brady (to Henry): Does j exist? 

Henry: Does j exist? I mean, does any number exist? 

End Slate

"Do numbers exist?" Preview: So what we're going to be talking about today is  whether or not numbers exist. And we're going to be thinking about three different schools of thought on that.

More from Brady: Don't forget to leave your favorite number and the reason under the video. And if you're wondering what I'm gonna do with this, well I don't exactly know yet, but when I decide, I'll probably let you know via the Numberphile Facebook and Twitter, so make sure you're following us on there.