There is no end to the types of numbers that we can introduce by giving a name to the numbers n that bear a certain relationship to the aliquot function. As we have already mentioned, n is perfect if a(n)=n and abundant if a(n) n. A semiperfect number n is one that is the sum of some of its proper divisors(those less than n), so it follows from the definition that all semiperfect numbers are either perfect or abundant. For example, 18 is semiperfect as 18=3+6+9. A number is called weird if it is abundant but not semi perfect, and the smallest weird number is 7o