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C# Program to check if a number is prime or not
To calculate whether a number is prime or not, we have used a for loop. Within that on every iteration, we use an if statement to find that the remainder is equal to 0, between the number itself.
for (int i = 1; i <= n; i++) { if (n % i == 0) { a++; } }
A counter a is also added, which increments only twice if the number is prime i.e. with 1 and the number itself. Therefore, if the value of a is 2, that would mean the number is prime.
Example
Let us see the complete example to check if a number is prime or not
using System; namespace Demo { class MyApplication { public static void Main() { int n = 5, a = 0; for (int i = 1; i <= n; i++) { if (n % i == 0) { a++; } } if (a == 2) { Console.WriteLine("{0} is a Prime Number", n); } else { Console.WriteLine("Not a Prime Number"); } Console.ReadLine(); } } }
Output
5 is a Prime Number
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