n)+Composite+Number

posted by: Germela =Composite number=

From Wikipedia, the free encyclopedia
A **composite number** is a positve which has a positive [|divisor] other than one or itself. In other words, if 0 < //n// is an integer and there are integers 1 < //a//, //b// < //n// such that //n// = //a// × //b// then //n// is composite. By definition, every integer greater than [|one] is either a [|prime number] or a composite number. The number one is a [|unit] - it is neither prime nor composite. For example, the integer 14 is a composite number because it can be factored as 2 × 7. The first 88 composite numbers (sequence [|A002808] in [|OEIS]) are 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 102, 104, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119. Every composite number can be written as the product of 2 or more (not necessarily distinct) primes; furthermore, this representation is unique up to the order of the factors.The Wilson's theorum provides a test for whether a number is prime or composite: 

Types of composite numbers
One way to classify composite numbers is by counting the number of prime factors. A composite number with two prime factors is a semiprime or 2-almost prime (the factors need not be distinct, hence squares of primes are included). A composite number with three distinct prime factors is a sphenic number. In some applications, it is necessary to differentiate between composite numbers with an odd number of distinct prime factors and those with an even number of distinct prime factors. For the latter  (where μ is the Möbius function and //x// is half the total of prime factors), while for the former  Note however that for prime numbers the function also returns -1, and that μ(1) = 1. For a number //n// with one or more repeated prime factors, μ(//n//) = 0. If //all// the prime factors of a number are repeated it is called a powerful nymber. If //none// of its prime factors are repeated, it is called __ squarefree __. (All prime numbers and 1 are squarefree.) Another way to classify composite numbers is by counting the number of divisors. All composite numbers have at least three divisors. In the case of squares of primes, those divisors are {1,//p//,//p//2}. A number //n// that has more divisors than any //x// < //n// is a [|highly composite number] (though the first two such numbers are 2&3)

Can be found on [|**www.wikipedia.com**]