C++ Programming Code Examples C++ > Mathematics Code Examples Check the Number is Prime or Not Check the Number is Prime or Not To check whether the number is a prime number or not a prime number in C++ programming, you have to ask to the user to enter a number and start checking for prime number. If number is divisible by 2 to one less than that number (n-1), then the number is not prime number, otherwise it will be a prime number. #include<iostream.h> #include<conio.h> void main() { clrscr(); int num,i,count=0; cout<<"Enter a number:"; cin>>num; for(i=2;i<num;i++) { if(num%i==0) { count++; break; } } if(count==0) { cout<<"This is a prime number"; } else { cout<<"This is not a prime number"; } getch(); }