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A prime number which equals prime numbers

  1. Jul 25, 2003 #1


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    how can i proove or disproove that the sum of a prime numbers which equals to other prime numbers is a prime number?
    i hope the question has been comprehended.
    Last edited: Jul 25, 2003
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  3. Jul 25, 2003 #2


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    Your hope is in vain, at least in my case.

    Let's see. 2+5 = 7 so the sum is prime. But 2+7 = 9, Oops.

    Maybe successive primes? 2+5 = 7, 5+7 =12 Oops.

    Maybe give an example?
  4. Jul 25, 2003 #3


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    i dont mean all the primes just a few.
    those who does follow the statement.
    Last edited: Jul 25, 2003
  5. Jul 25, 2003 #4


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    Please give an example:

    "the sum of a prime numbers which equals to other prime numbers "
    do you mean things like "2+ 5= 7", "9+ 2= 11", "5+ 7+ 11= 23"?

    "is a prime number?" Is WHAT a prime a number?

    My first reaction was that you meant the sum: well, of course, that's a prime- you just said it was!

    I THINK you mean that the number of primes in the sum must be a prime. I'll have to think of that. Can we find 4 primes whose sum is a prime?
  6. Jul 25, 2003 #5
    All primes except 2 are odd. So if you add two of them, the result is even, and thus not a prime.
  7. Jul 26, 2003 #6


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    9 isnt a prime.
    example the sum of:
    if you sum them you dont get a prime 25 and thus you disproove the statement what i want is a generalized proof not munerical.
    edit: a counter example is like 2 and 3 which are prime but they dont equal to other primes.
    Last edited: Jul 26, 2003
  8. Jul 26, 2003 #7
    I don't know about others, but i don't understand what you mean by that.

    Now, what i understand from what you previsouly said is that (in some cases) you can add up primes to reach another prime number. Now, some have showed that this is not always possible, some it is only possible in some cases.
    What you want to proove is that (the fact sometimes you can add up primes to end up with primes).
    So, in other words, if you take some primes, and add them up, you will reach one of two results :
    1-a non-prime number
    2-a prime number
    You are choosing part 2 to study, and want to proove it.
    What u are trying to proove is prooved by definition :smile:, you are saying that "among the add up of primes, i want to proove that those with a prime number result are prime numbers".
    It is like saying "proove that primes are primes", which is proven by definition.
    Maybe i didn't understand your question though.
  9. Jul 26, 2003 #8


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    no that's not what i want to find.
    what i want to find is the sum of the prime numbers which equal other prime numbers and proove it or disproove it for the genral view, for example:

    the sum of them is equal to prime number: 199.
  10. Jul 26, 2003 #9

  11. Jul 27, 2003 #10


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    At first I thought the problem was that I didn't know what you were saying.

    Now, I think the problem is that YOU don't know what you are saying!

    Yes, the sum of SOME primes is prime. The sum of other primes is NOT.

    It makes no sense to say that you want a GENERAL proof of something that is NOT generally true!

    You may mean that you want to find conditions on the original set of primes so that you will know that the sum must be prime.

    That is so general I doubt that you will find any simple conditions.
  12. Jul 21, 2009 #11
    This is an old thread - but just for the record:

    3+11+61= 75 (not 71)

    therefore 61+67+75= 203 which is not a prime.
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