Aliquot Sequences - Juan L. Varona's work on aliquot sequences examines sequences with start values up to 10000, and traces them to large composite values.

John Voight - Includes his thesis on the nonexistence or otherwise of odd perfect numbers and the use of continued fraction methods.

Multiperfect Number Search - Sources and binaries of Jason Moxham's searching software.

Multiply Perfect Numbers - Up-to-date information on multiperfect numbers and searchable database maintained by Achim Flammenkamp.

Perfect, Amicable and Sociable Numbers - Definitions, links and references of various applications of the sum of divisors function s(n).

The Perfect Number Journey - A Mathematics Enrichment Workshop introducing perfect numbers. Lessons and exercises extend over several pages. Aimed at interested middle and high school students.

Tables of Aliquot Cycles - Data for various kinds up to 10^12, including unitary, infinitary, exponential, augmented and reduced varieties.

Perfect Numbers - A detailed history of the quest for perfect numbers, from Euclid to their present-day Mersenne discoveries.

Aliquot Sequences - Results and software from Paul Zimmermann, addressing the Catalan Conjecture and working on the difficult "Lehmer Five" sequences.

Cubes of Perfection - From Ivars Peterson's MathTrek column in MAA Online. Curious relationships satisfied by perfect numbers.

Perfect Numbers - Harry J. Smith's pages of the mathematics behind perfection, aliquot sequences and Mersenne numbers. Includes program listings and e-mail archives.

On a Generalization of Perfect Numbers - J. L. Pe introduces perfect numbers relative to an arithmetical function f. Under this scheme, the usual perfect numbers are just one among many species of "f-perfect numbers". Several open problems and examples of perfect number sets are given, as well as a few f-amicable pairs.

Aliquot Sequences - Aliquot sequences arise in iterating the sum-of-divisors function s. Bosma has calculated tables up to start value 50,000 and 80 digits.