将num赋值给另一个变量，因为它的值已更改

import java.util.*;
class Example{
public static void main(String args[]){
    Scanner input=new Scanner(System.in);
    System.out.print("Input a prefer number :");
    int num=input.nextInt();
    int number  = num ; // assign to anaother variable as num gets changed 
    int reverse=0;
    while(num!=0){
        int num1=num%10;
        reverse=(reverse*10)+num1;
        num/=10;
    }

    System.out.println("Reverse num is "+reverse);
    if(number==reverse){
        System.out.println("The number is palindrome");
    }else{
        System.out.println("Try again");
    }
}

}

您可以考虑将数字视为字符串。
它允许任意大的数字。
然后可以使用stringbuilder反转字符串。

Scanner input=new Scanner(System.in);
            System.out.print("Input a preferred number :");
            String str = input.nextLine();
            StringBuilder sb = new StringBuilder(str);
            String reverse = sb.reverse().toString();
            System.out.println("Reverse num is "+reverse);
            if(str.equals(reverse)){
                System.out.println("The number is palindrome");
            }else{
                System.out.println("Try again");
            }
        }