What is Number theory: Definition and 471 Discussions

Number theory (or arithmetic or higher arithmetic in older usage) is a branch of pure mathematics devoted primarily to the study of the integers and integer-valued functions. German mathematician Carl Friedrich Gauss (1777–1855) said, "Mathematics is the queen of the sciences—and number theory is the queen of mathematics." Number theorists study prime numbers as well as the properties of mathematical objects made out of integers (for example, rational numbers) or defined as generalizations of the integers (for example, algebraic integers).
Integers can be considered either in themselves or as solutions to equations (Diophantine geometry). Questions in number theory are often best understood through the study of analytical objects (for example, the Riemann zeta function) that encode properties of the integers, primes or other number-theoretic objects in some fashion (analytic number theory). One may also study real numbers in relation to rational numbers, for example, as approximated by the latter (Diophantine approximation).
The older term for number theory is arithmetic. By the early twentieth century, it had been superseded by "number theory". (The word "arithmetic" is used by the general public to mean "elementary calculations"; it has also acquired other meanings in mathematical logic, as in Peano arithmetic, and computer science, as in floating point arithmetic.) The use of the term arithmetic for number theory regained some ground in the second half of the 20th century, arguably in part due to French influence. In particular, arithmetical is commonly preferred as an adjective to number-theoretic.

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  1. S

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    The Diophantine equation below, $$ x_0^{2} - (x_1^{2}+x_2^{2}+x_3^{2}+x_4^{2}+x_5^{2}+x_6^{2}+x_7^{2}+x_8^{2})=1$$ 1. Does above equation have any specific name? 2. What are the solutions(a formula)?? 3. in the case,$$x_8^{2}=0$$ , does anything special happen?? 4. What is the general way...
  2. S

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  3. S

    An equation of prime counting function

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  4. A

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  5. S

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  6. PsychonautQQ

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  7. PsychonautQQ

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  8. C

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  9. MidgetDwarf

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  10. M

    Help finding a topic in Number Theory

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  11. A

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  12. PsychonautQQ

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  13. M

    Understanding the Solution for Finding the Sum of Digits of m

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  14. PsychonautQQ

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  15. M

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  16. M

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  17. M

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  18. moriheru

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  20. Greg

    MHB Divisibility problem (number theory, I believe)

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  21. R

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  22. Medicol

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  23. camilus

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    ?
  24. evinda

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  25. Nono713

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  26. matqkks

    MHB Exploring Perfect Numbers: Applications & Intro to Number Theory

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  27. TheSodesa

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  28. D

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  29. Amcote

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  30. Jarvis323

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  31. Amcote

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  32. Islam Hassan

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  33. G

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  34. 1

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  35. X

    Studying Recommended Number Theory Textbooks?

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  36. chimath35

    Number Theory Theorems: Understanding Divisibility Rules

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  37. chimath35

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  38. chimath35

    Number Theory Help: Conjecture & Proof of 2^n-1 Not Prime

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  39. chimath35

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  40. chimath35

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  41. C

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  42. S

    MHB Find the least positive integer x such that x=5 (mod 7), x=7 (mod 11) and x=3(mod 13).

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  43. S

    MHB Therefore, the solutions are x = -1, 1, and 2 (mod 5).

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  44. chimath35

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  45. J

    Number Theory: Why always elementary proofs?

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  46. N

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  47. B

    Proving Divisibility Using Fermat's Theorem

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  48. chisigma

    MHB Unsolved analysis and number theory from other sites....

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  49. J

    What are the values of the remaining stamps?

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  50. F

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