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The tables below list all of the divisors of the numbers 1 to 1000. A divisor of an integer n is an integer m , for which n / m is again an integer (which is necessarily also a divisor of n ). For example, 3 is a divisor of 21, since 21/7 = 3 (and therefore 7 is also a divisor of 21).
[1] [5] [6] It is currently an open problem whether there are infinitely many Mersenne primes and even perfect numbers. [ 2 ] [ 6 ] The density of Mersenne primes is the subject of the Lenstra–Pomerance–Wagstaff conjecture , which states that the expected number of Mersenne primes less than some given x is ( e γ / log 2) × log log x ...
For example, 6 is highly composite because d(6)=4 and d(n)=1,2,2,3,2 for n=1,2,3,4,5 respectively. A related concept is that of a largely composite number , a positive integer that has at least as many divisors as all smaller positive integers.
The number of ways to choose 3 out of 8 objects or 5 out of 8 objects, if order does not matter. The sum of six consecutive primes (3 + 5 + 7 + 11 + 13 + 17) a tetranacci number [2] and as a multiple of 7 and 8, a pronic number. [3] Interestingly it is one of a few pronic numbers whose digits in decimal also are successive (5 and 6).
The integer 5 is a unitary divisor of 60, because 5 and = have only 1 as a common factor. On the contrary, 6 is a divisor but not a unitary divisor of 60, as 6 and 60 6 = 10 {\displaystyle {\frac {60}{6}}=10} have a common factor other than 1, namely 2.
Equivalently, it is a number for which the sum of proper divisors (or aliquot sum) is less than n. For example, the proper divisors of 8 are 1, 2, and 4, and their sum is less than 8, so 8 is deficient. Denoting by σ(n) the sum of divisors, the value 2n – σ(n) is called the number's deficiency.
The divisors of n are all products of some or all prime factors of n (including the empty product 1 of no prime factors). The number of divisors can be computed by increasing all multiplicities by 1 and then multiplying them. Divisors and properties related to divisors are shown in table of divisors.
The group of all Weil divisors is denoted Div(X). A Weil divisor D is effective if all the coefficients are non-negative. One writes D ≥ D′ if the difference D − D′ is effective. For example, a divisor on an algebraic curve over a field is a formal sum of finitely many closed points.