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Asked: 2026-06-07T11:34:57+00:00

I’ve got a simple problem, but somehow fail to solve it properly : I

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I’ve got a simple problem, but somehow fail to solve it properly :

I would like to test the primality of long long integers (64bits).
The primality requirement comes from the mixing of several hash values; if not respected, there is some kind of “echo” in the resulting output, which degrades the distribution property of the hash formula.

I’ve got a few interesting candidates, but cannot test at this stage their primality.

I’ve found a website which proposes just that :
input a number, and it provides the next value which is prime.
The problem is, this website only works for values within the 32 bits range limit.

I’ve been roaming SO for the same question, and it was asked several times already. However, all answers i’ve been consulting up to now only points towards methods and algorithms (such as miller rabin, or AKS), carrying a hidden “do-it-yourself” tag.

And that’s not what i’m looking for. I do not need to test primality regularly every day from now on, or for a huge numbers of candidates. I just have this need now, and for a very limited number of candidates.
Therefore a Ready-to-use tool which answer just this question (preferably, an online one), would better fit the bill.

But does that exist ?

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1 Answer

  1. Editorial Team

    You can plug in your number at http://www.alpertron.com.ar/ECM.HTM, which will tell you if it is prime or give you its factors if it is not. Or you could use the Factors[n] function at http://www.wolframalpha.com, which does the same thing. Either can quickly handle 64-bit integers.

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