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Prime number: A positive integer with exactly two positive divisors: itself and 1. The primes form an infinite sequence 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, ... Composite number: A positive integer that can be factored into a product of smaller positive integers. Every integer greater than one is either prime or composite.
In a complex plane, > is identified with the positive real axis, and is usually drawn as a horizontal ray. This ray is used as reference in the polar form of a complex number . The real positive axis corresponds to complex numbers z = | z | e i φ , {\displaystyle z=|z|\mathrm {e} ^{\mathrm {i} \varphi },} with argument φ = 0. {\displaystyle ...
[12] [13] Only positive integers were considered, making the term synonymous with the natural numbers. The definition of integer expanded over time to include negative numbers as their usefulness was recognized. [14] For example Leonhard Euler in his 1765 Elements of Algebra defined integers to include both positive and negative numbers. [15]
The modern definition of "prime number" is "positive integer with exactly 2 factors", so 1 is not prime. This definition can be rationalized by observing that it more naturally suits mathematical theorems that concern the primes. For example, the fundamental theorem of arithmetic is easier to state when 1 is not considered prime. [11]
Every positive real number x has a positive square root, that is, there exist a positive real number such that =. Every univariate polynomial of odd degree with real coefficients has at least one real root (if the leading coefficient is positive, take the least upper bound of real numbers for which the value of the polynomial is negative).
A powerful number is a positive integer m such that for every prime number p dividing m, p 2 also divides m. Equivalently, a powerful number is the product of a square and a cube, that is, a number m of the form m = a 2 b 3, where a and b are positive integers. Powerful numbers are also known as squareful, square-full, or 2-full.
Fermat polygonal number theorem, that every positive integer is a sum of at most n of the n-gonal numbers Waring–Goldbach problem , the problem of representing numbers as sums of powers of primes Subset sum problem , an algorithmic problem that can be used to find the shortest representation of a given number as a sum of powers
In number theory, a polite number is a positive integer that can be written as the sum of two or more consecutive positive integers. A positive integer which is not polite is called impolite. [1] [2] The impolite numbers are exactly the powers of two, and the polite numbers are the natural numbers that are not powers of two.