Re: How many Prime numbers
 From: "Tim Peters" <tim.one@xxxxxxxxxxx>
 Date: Tue, 3 Oct 2006 17:25:44 0400
[L]
I have been trying to find out how many prime numbers there are in 2 to
128 power. I am sure this number is available somewhere but I have
been luckless in finding it.
[Tim Peters]
Nobody knows, exactly, and nobody is likely to know for many years
to come:
http://primes.utm.edu/howmany.shtml
AFAIK, it's still the case that the largest n for which pi(n) is known
exactly is n = 4*10^22 (your 2^128 ~= 3.4*10^38, much larger). That took
about 250 CPUdays to compute using the fastest known algorithm:
http://numbers.computation.free.fr/Constants/Primes/Pix/results.html
[L]
I assume that means a 128 bit code is almost fool (poor choice) proof.
Sorry, I don't know what you mean by "a 128 bit code". The exact number of
primes <= n isn't relevant to any codes I'm aware of. Any system relying
on, e.g., that it's difficult to /factor/ 128bit integers is worthless,
because modern methods can factor integers of that size quickly. But I
don't know if that's relevant to what you intended to ask ;)
.
 References:
 How many Prime numbers
 From: L
 Re: How many Prime numbers
 From: Tim Peters
 Re: How many Prime numbers
 From: L
 How many Prime numbers
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