Is one considered a prime number?

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Discussion Overview

The discussion centers around whether the number one is considered a prime number. Participants explore definitions, implications for mathematical theorems, and the uniqueness of prime factorization, with a focus on theoretical and conceptual aspects.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants argue that the definition of a prime number, which includes having exactly two distinct positive divisors, excludes one.
  • Others suggest that not considering one as prime is a matter of convenience to maintain the uniqueness of prime factorization in number theory.
  • A participant notes that including one as a prime would lead to multiple valid prime factorizations for the same number, which contradicts established mathematical results.
  • One participant expresses interest in further reading on prime numbers, indicating a desire for deeper understanding of the topic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether one should be classified as a prime number, with multiple competing views presented regarding definitions and implications.

Contextual Notes

The discussion highlights the dependence on definitions and the implications of those definitions for mathematical theorems and properties, without resolving these complexities.

mateomy
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Is one considered a prime number? I know the definition of a prime number is any number that is constituted only by 1 and itself; does this include one? Why or why not?
 
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It is mainly a matter of convenience not to call 1 a prime. Otherwise many theorems involving prime numbers would have to say "excluding 1". For example every integer can be expressed uniquely as a product of powers of primes. If you included 1, you would have to say "except 1" to have uniqueness.
 


No, 1 is not a prime number. This is quite an arbitrary definition, but there are good reasons not to define 1 a prime number.

For example, every number has a unique prime factorization, eg

60=2².3.5

But if 1 is a prime, then this is not true anymore, because

60=2².3.5.1

is then another prime factorization.

There are another quite nice results for which 1 should not be prime. So 1 is not prime. A prime number is in fact, by definition, a number with exactly two divisors. This definition would exclude 1.
 


Oh okay, that makes sense. Does anyone have any reading suggestions on primes specifically. I just started reading "Elementary Theory of Numbers" by LeVeque. Any critiques on this, or pointers to another text perhaps?

Thanks.
 

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