1. Find no. of digits in a number

public static int count_no(int n) {
        int c = 0;
        while (n != 0) {
            n = n/10;
            c++;
        }
        return c;
    }

1. Palindrome Number Eg➖121,131

public static boolean isPalin(int n){
        int rev = 0;
        int temp = n;
        while (temp != 0) {
            int last_digit = temp%10;
            rev = rev * 10 + last_digit;
            temp = temp/10;
        }
        // if (n == rev) {
        //     return true;
        // }
        // return false;
        return (rev == n);
    }

1. factorial of a Number

public static int fact(int n) {
        if (n == 0 ) {
            return 1;
        }
        
        return n * fact(n-1);
    }

1. Trailing Zeros in Factorial of n {Eg➖5 → 1} 120*

int sum = 0;
        while(n > 0){
            n = n/5;
             sum = sum + n;
        }
        return sum;

1. Greatest Common Divisor

int ans = Math.min(a, b);
        while (ans>0) {
            if (a%ans == 0 && b%ans == 0) {
                break;
            }
            ans--;
        }
        return ans;

1. Euclidean Algorithm for {GCD}

int gcd(int a , int b){
 if(b == 0){
    return a;
    }else  {
   return gcd(b,a%b);
   }

1. LCM of Two Numbers → {Smallest no. which is divisible by both no}

public static int lcm(int a , int b) {
        int ans = Math.max(a, b);
        while (true) {
            if (ans%a == 0 && ans%b == 0) {
                return ans;
            }
            ans++;
        }
    }

1. Check Number is Prime or Not

public static boolean isPrime(int n) {
        if (n%2 == 0) {
            return false;
        }
        return true;
    }

1. Find Prime Factor of a Number

public static void primeFact(int n) {
        if (n <= 1) {
            return;
        }
        for (int i = 2; i <= Math.sqrt(n); i++) {
            while (n%i == 0) {
                System.out.println(i);
                n = n/i;
            }
        }
        if (n > 1) {
            System.out.println(n);
        }
    }

1. All Divisor of a Number