>>Ok today's number is 383... >>At last!
I know there's number of people have been demanding...
No one has been demanding 383. This is one...
'Cause numberphile has, you know, grown over the years.
And you've done all sorts of exciting numbers: e, pi...
All the all the big guys have been involved.
But now I feel like we're losing touch with our roots.
Not literal roots but like metaphorical.
The simple numbers which made this channel what it was
And I think 383 is not an amazing number.
It's not special number, or a great number.
But we can't forget about the numbers that are day in day out
making maths work. So,
the work horses of the number system.
383 is a prime.
That's already amazing!
It's already amazing.
It's also a palindrome.
Which is quite nice.
It is the sum of the first 3 palindromic 3-digit primes.
And so if you get the first 3,
I think it's 101 is a 3-digit palindrome +
131 3-digit palindromic prime
+ 151 is the next one,
that's the first 3 of them that equals 383.
That's kind of cool. There's something going on there.
You're not doing a very good job, making me think it isn't a special number.
Well this is the great thing about numbers.
Any semi-arbitrary number, if you dig into it, it's gonna have some cool properties.
It's also the smallest number which is the sum of a prime and the reversal of the prime:
241 is a prime number
and if you add it to its digits in reverse order 142
it equals 383 which is itself prime.
So the smallest number which is prime
and it's a prime number plus
the reverse of the digits of that prime number in base 10.
That's kind of cool. That's a thing.
It's a bit base ten-ny.
In fact anything involving palindroms is a little bit base ten-ny.
though, what will you gonna do?
It's also a thing called a Woodall prime.
And a Woodall prime... let's that so...good to get a different color...
A Woodall prime is a prime number.
So Mersenne primes....
We all know and love Mersenne primes 2^n - 1.
A Woodall prime is n2^n - 1.
This is a Woodall prime
It's the 3rd Woodall prime. It is 6 x 2^6 - 1 = 383.
>>And so if... >>Did you forgot the ending 3 ?
I forgot the ending 3. I've been doing a lot today videos, you know
And the fact is that number is a palindrom but I've written over half of it, so I've got no excuses.
So anyway right...
Woodall primes again, an unsung type of prime.
Completely go on and on; we've done so many videos about Mersenne primes.
Don't get me wrong, big fan.
Woodall primes, have you ever heard them mentioned?
I never hear them mentioned. I think they're great.
And we do videos whenever we find a new Mersenne prime
cos' they're the big ones. Everyone celebrates Mersenne primes.
We did a video when I printed it out. It was possibly over-the-top.
Woodall primes, did you remember the last time we had a Woodal prime?
See? No one does right? and yet we are still trying to find them.
So quick bit of history.
They were first named or used by Woodall,
In fact, it was two guys, it was Cunningham and Woodhall in 1917.
Which you will notice it exactly 100 years ago and so this is the centenary
We're in the centenary year of Woodall primes.
And I imagine I mean a lot of people may be organizing Woodall prime parties.
But I haven't been invited and I haven't heard about them.
>>Matt, if it was one guy going, you'd be... >>It's well-- I'd better be-- I'll be a little bit offended if I wasn't...
And so,
I think in the centenary year of Woodall primes,
we should celebrate the less significant
the less exciting the less well known
types of numbers.
And so, 383 as a Woodall prime, I think we should be celebrating it
in 1917. And what we can do
other than having parties, if you want to celebrate it,
is to help us find another one.
The last time we found a world record
Woodall prime was in 2007
So the last one we found was in the 90th anniversary of Woodall primes.
Wouldn't it be great to find another one
in the 100-year anniversary?
On case you're wondering, the last one we found,
the world record, is
3,752,948
- get that right - times 2^3,752,948 - 1.
That a prime number and it has over a million,
it's got 1,129,757 digits.
That is a lot, that is the current biggest known Woodall prime.
So I think we should try and find a better one.
That was found, not by the great internet Mersenne prime search
because in their name as you can tell they're
all that Mersenne numbers.
They have no respect, they don't give any attention
to the smaller types of primes.
There is another organization called PrimeGrid.
And PrimeGrid deal with all the other primes
that the Mersenne guys forgot about.
So people are running a very simple thing
you can download the thing, you run it on your computer,
your computer would check bigger and bigger Woodall numbers,
to see if any of them are prime
if enough computers maybe will do PrimeGrid, I mean i do.
As I speak there is a computer in my office,
that I built solely to run PrimeGrid
to try and find... I haven't found any yet...
to try and find these. And they do lots of other types of prime numbers.
You can let your computer in it's downtime help us celebrate
in the 100-year anniversary some unsung prime numbers.
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Most another to get all the glory partly because
they're linked to perfect numbers in
fact that's why we care about them in the first place.
And now it's because they're easy.
And they hold I think they've either got all or 9/10
of the top 10 biggest primes are all Mersenne primes, cos' they're easy to find, right.
And the people ch... peoples go for glory
all they care about are the biggest ones.
They go and pick off the Mersenne primes,
where these other ones, they're not as easy to find, right.
And they know that this is about...
Well this is well below, right.
This is an order of magnitude fewer digits
than the current world-record Mersenne prime.
And I think it's a shame
that we knew size isn't everything.
We should be looking for these other interesting numbers.