20060103, 00:34  #1 
"Jason Goatcher"
Mar 2005
DB1_{16} Posts 
What is the largest database of all primes from 2 up?
I thought I'd give you this question to chew on: If you start with 2 and find all primes in order, what is the biggest known database of this type?
I don't know the answer and I'm not sure how it would be discovered. I would also be interested in people's opinions of how big a hard drive you would need to store all the primes from 2 to, say, 2^100 in uncompressed form with a byte between them. 
20060103, 00:45  #2  
"Mike"
Aug 2002
2·3,931 Posts 
Quote:
especially post #9 http://www.mersenneforum.org/showthread.php?t=1768 

20060103, 20:54  #3  
Mar 2005
252_{8} Posts 
Quote:
http://www.primenumbers.org/ on a related topic, a friend asked me a while back what is the smallest number whose prime/compositeness is unknown. I think the question although seemingly sensible, doesn't have a simple, sensible answer. Richard Last fiddled with by Richard Cameron on 20060103 at 20:54 

20060103, 21:35  #4 
"Nancy"
Aug 2002
Alexandria
2,467 Posts 
There isn't much point in storing a list of prime numbers. They can be generated much more quickly than such a list could be transferred over a network. Look for Bernstein's primegen library, afaik it can generate primes up to about 10^18. There are about 24*10^15 primes below 10^18, so keeping them in a database is out of the question.
Alex 
20060104, 01:30  #5  
"Jason Goatcher"
Mar 2005
5×701 Posts 
Quote:
x/log x gives the answer of about 3.33333...^29th power. Assuming a terabye is 10^12, that means it would take 1/3rd of a megateraterabye. Now assuming a square inch can take up a gigabyte(which I don't believe has actually happened yet, but probably will), the hard drive would take up 3.333...*10^20th power inches, which means 2.31...(481 repeated 5 times)...4*10^18 sq. feet, or 83032556201 sq. miles. The United States has an area of 3,619,969 sq. miles, which means the hard drive would cover a little more than 22937 United States. I was unable to find the sq. mileage of the earth, with or without water in my dictionary. Would anyone like me to calculate how fast the edge of this hard drive would spin at 7200 rpms, lol? Edit: error, I assumed every number took up a byte, but most of them are too big. Last fiddled with by jasong on 20060104 at 01:38 

20060104, 19:04  #6  
Jun 2005
Near Beetlegeuse
2^{2}·97 Posts 
Quote:


20060104, 23:16  #7  
"Richard B. Woods"
Aug 2002
Wisconsin USA
1111000001100_{2} Posts 
Quote:
Quote:
Mean radius of Earth is 3960 miles => ~2*10^{8} sq. miles surface area. 

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