
The largest known prime number has emerged. It has more than 23M digits - digital55
https://www.washingtonpost.com/national/health-science/the-largest-known-prime-number-has-emerged-it-has-more-than-23-million-digits/2018/01/12/e641cef0-f6e2-11e7-beb6-c8d48830c54d_story.html
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SurrealSoul
>"Anyone can download the software free. So you, too, could discover a record-
breaking prime number — if you have enough patience."

Maybe mining zcash is lucrative, but finding a new big prime number sounds
pretty nice

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eternalcode
I wish we can collectively "mine" solutions for questions that are currently
un-solved.

Like Larger prime number, or create a hive mind that acts as an AI.

~~~
SketchySeaBeast
Isn't that the point of projects like folding@home?

And hive mind AI is literally skynet.

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pavel_lishin
The Borg would be a better analogy; Skynet was just an AI with a specific
purpose, no hive-mind about it.

~~~
SketchySeaBeast
Well that's more reassuring.

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pronoiac
There's a site for large prime numbers, and I wondered Mersenne primes have
been the largest primes known - since 1992, and since 1952 with an exception
for 1989 to 1992. GIMPS - [https://www.mersenne.org](https://www.mersenne.org)
\- has topped the list since 1996.

[https://primes.utm.edu/notes/by_year.html#table2](https://primes.utm.edu/notes/by_year.html#table2)

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TekMol
I have two questions:

1: How do we know it's the largest known prime number? What qualifies as a
'known' prime number? Is there an official registry somewhere?

2: Are all prime numbers smaller then this one also known? Or could somebody
still come up with an unknown 'not very large prime number'?

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colbyh
1\. Essentially, yes there's a list. Since there doesn't exist a higher level
formula to identify primes it's been verified by some variation of a brute
force method.

2\. That all smaller primes are known can't be verified. Primes of this size
are usually found by a number of formulas that find "likely" primes and then
verified by brute force (afaik). Because of that fuzzy match to start there
might be smaller primes that haven't yet been identified.

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planteen
Calling it brute force isn't quite right. There is an efficient algorithm for
prime determination (Lucas-Lehmer primality test) on Mersenne Primes (numbers
of the form 2^p-1).

[https://en.wikipedia.org/wiki/Lucas–Lehmer_primality_test](https://en.wikipedia.org/wiki/Lucas–Lehmer_primality_test)

~~~
colbyh
Thanks for the reminder! And this is my bad because I was paywalled on my
phone and didn't see that it was, in fact, a mersenne prime that was found.

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thsowers
Previous discussion:
[https://news.ycombinator.com/item?id=16063946](https://news.ycombinator.com/item?id=16063946)

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auggierose
Given that we know that there are infinitely many primes, why are we
interested in knowing ever larger ones?

It's somewhat like asking, what is the largest known natural number?

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p1mrx
If nothing else, "what's the largest prime number you've found?" would be a
fun question to ask another intelligent civilization, should we make contact
with one.

~~~
auggierose
Alright, that's a good one :)

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cnvogel
Quote from the Article: """The figure is calculated by multiplying 2 by itself
77,232,917 times and then subtracting 1."""

Would HN agree that multiplying 2 by itself once is 2⨯2 = pow(2,2), twice is
2⨯2⨯2 = pow(2,3) and N times yields pow(2,N+1)?

The Mersenne Prime found is pow(2,77232917) − 1, hence the article got the
number wrong?

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mattashii
If you're going that way, you can also interpret it - pardon my programming -
as the following:

    
    
      int result; 
      for (int i = 0; i < 77232917; i++) { 
          result = 2 * 2; 
      } 
      return result - 1; 
    

... which obviously results in 3. Also a (mersienne) prime, but not quite as
big as you'd expect, and certainly not millions of digits long.

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nopacience

      int result; 
      for (int i = 0; i < 77232917; i++) { 
          result = 2 * 2; <----- you basically said result=4 77232917 times 
      } 
      return result - 1; <--- and then 4-1=3
    

so of course it will always be 3

~~~
colanderman
That is the joke.

