In mathematics, a colossally abundant number (sometimes abbreviated as CA) is a certain kind of natural number. Formally, a number n is colossally abundant iff there is an ε > 0 such that for all k > 1,
where σ denotes the divisor function. The first few colossally abundant numbers are 2, 6, 12, 60, 120, 360, 2520, 5040, ... ; all colossally abundant number are also superabundant numbers, but the converse is not generally true.
Properties
All colossally abundant numbers are Harshad numbers.
Relation to the Riemann hypothesis
Colossally abundant numbers are related to the Riemann hypothesis (someone should fill in details for this).
Also see