Composite Number Program

A composite number is a positive integer that is not prime. In other words, it has a positive divisor other than one or itself. First few composite numbers are 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, ......... 

• 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.

How to check if a given number is a composite number or not? 
Examples:

Input : n = 21
Output: Yes
The number is a composite number!

Input : n = 11
Output : No

The idea is simple, we can use any of the below methods used for prime checking. We just need to change return statements. Return true is changed to return false and vice versa. 

• Primality Test | Set 1 (Introduction and School Method)
• Primality Test | Set 2 (Fermat Method)
• Primality Test | Set 3 (Miller–Rabin)

In below code optimized school method is discussed. 

Output: 

false
true

Time Complexity:- O(sqrt(n))

Space Complexity:-O(1)

Program on Composite Numbers

• Find a range of composite numbers of given length
• Generate a list of n consecutive composite numbers (An interesting method)
• Sum and product of k smallest and k largest composite numbers in the array
• Product of all the Composite Numbers in an array
• Count and Sum of composite elements in an array
• Split n into maximum composite numbers

Reference :
https://en.wikipedia.org/wiki/Composite_number