Number theory addresses problems about integer and rational numbers. It includes congruences, divisibility, primes, and Fermat's Last Theorem.
This category includes topics that focus on the properties of numbers such as prime numbers and divisibility.

## Algebraic

Algebraic Theory of Numbers.

## Chats and Forums

Mailing lists, newsgroups, forums, message boards, and chat rooms for discussing topics in Number Theory.
Please submit only websites that have English language content to this category and its subcategories. If your site is in a language other than English, please submit it to the appropriate category of World.

## Computational

Algorithmic, or Computational, Number Theory studies algorithms for performing number theoretic calculations such as highest common factor, factorisation or testing for primality.

## Diophantine Equations

In this category are included any equation or set of equations where the unknowns must be integer numbers. It includes Fermat Last Theorem as a special case.

## Education

Educational Resources covers lecture notes, web texts, course materials, project work -- all within the field of Number Theory at the undergraduate or postgraduate level.

## Elliptic Curves and Modular Forms

Elliptic Curves are related to the solutions to equations y^2 = x^3 + A x + B in the field of rationals, algebraic extensions of the rationals, p-adic rational numbers, or a finite field. They are used in factorization of integers and also played a role in the recent resolution of the conjecture known as Fermat's Last Theorem.

Please submit only sites of theoretical content in the subject of elliptic curves and modular forms. This may include applications of such theory, such as their usage in primality proving, factorization, and cryptography - however in these cases consider carefully whether the site is more suited to those categories in the Open Directory Project. Software programs and tables should be submitted to the appropriate subcategory.

## Events

Conferences, courses, meetings, seminars,workshops and other events in the Theory of Numbers.

## Factoring

Factoring numbers is a concept learnt with the introduction of divisibility in schools, yet the process can be exceptionally challenging and difficult. This category addresses topics from the basic divisibility tests to perfection and the general problem of extracting prime factors.
Please submit sites relating to divisibility, factoring projects and status, methods and algorithms. Please note that factoring software should be submitted to Science/Math/Number_Theory/Software.

## Open Problems

Unsolved problems in Number Theory

## Organizations

Sites of professional and academic organizations, including national and international organizations, related to the mathematical discipline of Number Theory.
This category is only for sites of professional and academic organizations related to the mathematical discipline of Number Theory.
All sites in this category should be in English. Sites in other languages can be listed in the appropriate subcategory of

## People

Researchers in Number Theory.
Please observe the following suggestion when submitting sites to the category:
a. Submit the mathematician/researcher''s name as the title (in last name, first name format)
b. Description should include, in this order: place of work, field of research or interest, content of the site.

## Publications

Books, journals and preprints in Number Theory
This category is for web sites which contain material complementing printed books, for example with software, tables or errata. Online texts are also welcome. Please do not submit pages which merely announce or advertise books. Please submit publishers'' sites to Science/Math/Publications/Book_Publishers.

## Research Groups

Research groups, laboratories and networks in Number Theory