In mathematics, a multiply perfect number (also called multiperfect number or pluperfect number) is a generalization of a perfect number.
For a given natural number k, a number n is called k-perfect (or k-fold perfect) if and only if the sum of all positive divisors of n (the divisor function, σ(n)) is equal to kn; a number is thus perfect if and only if it is 2-perfect. A number that is k-perfect for a certain k is called a multiply perfect number. As of July 2004, k-perfect numbers are known for each value of k up to 11.
It can be proven that:
- For a given prime number p, if n is p-perfect and p does not divide n, then pn is (p+1)-perfect. This implies that an integer n is a 3-perfect number divisible by 2 but not by 4, if and only if n/2 is an odd perfect number, of which none are known.
- If 3n is 4k-perfect and 3 does not divide n, then n is 3k-perfect.
Read more about Multiply Perfect Number: Smallest k-perfect Numbers
Famous quotes containing the words multiply, perfect and/or number:
“The uselessness and expensiveness of modern women multiply bachelors.”
—Samuel Richardson (1689–1761)
“A single thankful thought towards heaven is the most perfect of all prayers.”
—Gotthold Ephraim Lessing (1729–1881)
“If I could live as a tree, as a river, as the moon, as the sun, as a star, as the earth, as a rock, I would. ...Writing permits me to experience life as any number of strange creations.”
—Alice Walker (b. 1944)