Superior highly composite number

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Divisibility-based sets of integers

Form of factorization:

Prime number

Composite number

Powerful number

Square-free number

Achilles number

Constrained divisor sums:

Perfect number

Almost perfect number

Quasiperfect number

Multiply perfect number

Hyperperfect number

Superperfect number

Unitary perfect number

Semiperfect number

Primitive semiperfect number

Practical number

Numbers with many divisors:

Abundant number

Highly abundant number

Superabundant number

Colossally abundant number

Highly composite number

Superior highly composite number

Other:

Deficient number

Weird number

Amicable number

Friendly number

Sociable number

Solitary number

Sublime number

Harmonic divisor number

Frugal number

Equidigital number

Extravagant number

See also:

Divisor function

Divisor

Prime factor

Factorization

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In mathematics, a superior highly composite number is a certain kind of natural number with the following properties. A natural number n is called superior highly composite iff there is an ε > 0 such that for all natural numbers k ≥ 1,

where d(n), the divisor function, denotes the number of divisors of n. The first few superior highly composite numbers are 2, 6, 12, 60, 120, 360, 2520, 5040, 55440, 720720, 1441440, 4324320, 21621600, 367567200... (sequence A002201 in OEIS).

[edit] Properties

All superior highly composite numbers are highly composite; it can also be shown that there exist prime numbers π₁, π₂, ... such that the n-th superior highly composite number s_n can be written as

The first few π_n are 2, 3, 2, 5, 2, 3, 7, ... (sequence A000705 in OEIS).

[edit] References

• Srinivasa Ramanujan, Highly Composite Numbers, Proc. London Math. Soc. 14, 347-407, 1915; reprinted in Collected Papers (Ed. G. H. Hardy et al.), New York: Chelsea, pp. 78–129, 1962
• Weistein, Eric W., "Superior highly composite number" from MathWorld.