C Program to Reverse a Number

In this example, you will learn to reverse the number entered by the user.

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To understand this example, you should have the knowledge of the following C programming topics:

Reverse an Integer

#include 
int main() {
    int n, rev = 0, remainder;
    printf("Enter an integer: ");
    scanf("%d", &n);
    while (n != 0) {
        remainder = n % 10;
        rev = rev * 10 + remainder;
        n /= 10;
    }
    printf("Reversed number = %d", rev);
    return 0;
}

Output

Enter an integer: 2345
Reversed number = 5432

This program takes an integer input from the user. Then the while loop is used until n != 0 is false (0).

In each iteration of the loop, the remainder when n is divided by 10 is calculated and the value of n is reduced by 10 times.

Inside the loop, the reversed number is computed using:

rev = rev*10 + remainder;