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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.programming
Subject: Re: Where can I find maximum primes < 2^n
Date: Wed, 15 May 2019 23:23:48 +0100
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Bonita Montero <Bonita.Montero@gmail.com> writes:

> I need the largest prime that fits in a unsigned 64 bit integeger
> to  build hash-keys. Can anyone tell me a source for such primes
> in the net?

That's been answered, but there are also many programs that can tell
you.  For example, it's common for computer maths programs to have next
and previous prime functions.  For example, GP/PARI reports

? precprime(2^64 - 1)
%1 = 18446744073709551557

as does Maxima.

-- 
Ben.