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  2. Euclid's theorem - Wikipedia

    en.wikipedia.org/wiki/Euclid's_theorem

    [2] Consider any finite list of prime numbers p 1, p 2, ..., p n. It will be shown that there exists at least one additional prime number not included in this list. Let P be the product of all the prime numbers in the list: P = p 1 p 2...p n. Let q = P + 1. Then q is either prime or not:

  3. Prime number theorem - Wikipedia

    en.wikipedia.org/wiki/Prime_number_theorem

    Except for 2 and 5, all prime numbers end in 1, 3, 7, or 9. Dirichlet's theorem states that asymptotically, 25% of all primes end in each of these four digits. However, empirical evidence shows that the number of primes that end in 3 or 7 less than n tends to be slightly bigger than the number of primes that end in 1 or 9 less than n (a ...

  4. Prime number - Wikipedia

    en.wikipedia.org/wiki/Prime_number

    A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways of writing it as a product, 1 × 5 or 5 × 1, involve 5 itself. However, 4 is composite because it is a ...

  5. Mersenne prime - Wikipedia

    en.wikipedia.org/wiki/Mersenne_prime

    Proof: 2 p+12 (mod q), so 2 ⁠ 1 / 2 ⁠ (p+1) is a square root of 2 mod q. By quadratic reciprocity, every prime modulus in which the number 2 has a square root is congruent to ±1 (mod 8). A Mersenne prime cannot be a Wieferich prime. Proof: We show if p = 2 m − 1 is a Mersenne prime, then the congruence 2 p−11 (mod p 2) does ...

  6. Euclid–Euler theorem - Wikipedia

    en.wikipedia.org/wiki/Euclid–Euler_theorem

    The Euclid–Euler theorem is a theorem in number theory that relates perfect numbers to Mersenne primes. It states that an even number is perfect if and only if it has the form 2p−1(2p − 1), where 2p − 1 is a prime number. The theorem is named after mathematicians Euclid and Leonhard Euler, who respectively proved the "if" and "only if ...

  7. Fundamental theorem of arithmetic - Wikipedia

    en.wikipedia.org/wiki/Fundamental_theorem_of...

    First, 2 is prime. Then, by strong induction, assume this is true for all numbers greater than 1 and less than n. If n is prime, there is nothing more to prove. Otherwise, there are integers a and b, where n = a b, and 1 < a ≤ b < n. By the induction hypothesis, a = p 1 p 2 ⋅⋅⋅ p j and b = q 1 q 2 ⋅⋅⋅ q k are products of primes.

  8. Bertrand's postulate - Wikipedia

    en.wikipedia.org/wiki/Bertrand's_postulate

    Bertrand's postulate. In number theory, Bertrand's postulate is the theorem that for any integer , there exists at least one prime number with. A less restrictive formulation is: for every , there is always at least one prime such that. Another formulation, where is the -th prime, is: for.

  9. Euclid's lemma - Wikipedia

    en.wikipedia.org/wiki/Euclid's_lemma

    Euclid's lemma. In algebra and number theory, Euclid's lemma is a lemma that captures a fundamental property of prime numbers: [note 1] Euclid's lemma — If a prime p divides the product ab of two integers a and b, then p must divide at least one of those integers a or b. For example, if p = 19, a = 133, b = 143, then ab = 133 × 143 = 19019 ...