unitary divisor
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Unitary divisor — In mathematics, a natural number a is a unitary divisor of a number b if a and frac{b}{a} are coprime, having no common factor other than 1. Thus, 5 is a unitary divisor of 60, because 5 and frac{60}{5}=12 have only 1 as a common factor, while 6… … Wikipedia
Divisor function — σ0(n) up to n = 250 Sigma function σ … Wikipedia
Unitary perfect number — A unitary perfect number is an integer which is the sum of its positive proper unitary divisors, not including the number itself. (A divisor d of a number n is a unitary divisor if d and n / d share no common factors.) Some perfect numbers are… … Wikipedia
Divisor — divisible redirects here. For divisibility of groups, see Divisible group. For the second operand of a division, see Division (mathematics). For divisors in algebraic geometry, see Divisor (algebraic geometry). For divisibility in the ring theory … Wikipedia
Harmonic divisor number — This article is about harmonic divisor numbers. For meanings of harmonic number, see harmonic number (disambiguation). In mathematics, a harmonic divisor number, or Ore number (named after Øystein Ore who defined it in 1948), is a positive… … Wikipedia
Perfect number — In number theory, a perfect number is a positive integer that is equal to the sum of its proper positive divisors, that is, the sum of its positive divisors excluding the number itself (also known as its aliquot sum). Equivalently, a perfect… … Wikipedia
Prime number — Prime redirects here. For other uses, see Prime (disambiguation). A prime number (or a prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. A natural number greater than 1 that is not a prime number is… … Wikipedia
Composite number — A composite number is a positive integer which has a positive divisor other than one or itself. In other words a composite number is any positive integer greater than one that is not a prime number. So, if n > 0 is an integer and… … Wikipedia
Highly composite number — This article is about numbers having many divisors. For numbers factorized only to powers of 2, 3, 5 and 7 (also named 7 smooth numbers), see Smooth number. A highly composite number (HCN) is a positive integer with more divisors than any… … Wikipedia
Multiply perfect number — 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… … Wikipedia
Deficient number — In number theory, a deficient number or defective number is a number n for which the sum of divisors σ(n)<2n, or, equivalently, the sum of proper divisors (or aliquot sum) s(n)<n. The value 2n − σ(n) (or n − s(n)) is… … Wikipedia
