Today we are going to write a program to check if a given number is a Prime number in C++ programming language i.e. if a number enter by user is a prime number or not.
We all know what a Prime number is let’s recall quickly:
Prime Number: A number which is divisible by 1 and itself is called Prime number i.e. it do not have any factors. Let’s see how to check Prime numbers in a program.
Problem: Check if the number input by user is Prime or not.
Logic behind finding prime number:
- Start finding the factors of the number from 1.
- Count the total number of factors.
- If number of factors are 2 then it is a Prime number otherwise not.
Program to check if a number is Prime number in C++:
#include<iostream> using namespace std; int main() { int number,count=0; cout<<"Enter a number: "; cin>>number; for(int a=1;a<=number;a++) { if(number%a==0) count++; } if(count==2) cout<<"t"<<number<<" IS A PRIME NUMBER \n"; else cout<<"t"<<number<<" IS NOT A PRIME NUMBER \n"; return 0; }
OUTPUT:
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