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Can negative numbers be Prime or Composite?

It makes no difference. Prime-ness has to do with multiplication / division. A number is prime if and only if it is divisible only by itself and the number '1'. Whether the sign is positive or negative does not matter. Since you ask about "primality" and so may be interested in number theory. You might be interested in a very "simple" conjecture (a mathematical statement that is surely "true" but which has never been proved. It is called Goldbach's conjecture. Every even number (that is one that is divisible by "2") is the sum of at least one pair of prime numbers. Examples: 2=1+1, 4=3+1, 6=5+1, 8=5+3 or 7+1, 12= 11+1 = 7+5 .... There may be more combinations of primes but there is always at least one. And just subtracting the number "1" does not always work. For example 10=9+1 is not an example because the number "9" is not prime, but 10=7+3 is a prime pair.

But no mathematical proof for this apparently "simple" theorem in number theory has been found. Funny thing these simple counting numbers.

Vince Calder

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