Check if a large number is divisible by 5 or not

Last Updated : 4 Jun, 2026

Given a number s in the form of string, the task is to check if the number is divisible by 5. 

Examples: 

Input : s = 56945255
Output : true

Input : s = 12345
Output : true

Input : s = 36358839596
Output : false

Try It Yourself
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Table of Content

[Naive Approach] String to Integer Conversion - O(n) Time and O(1) Space

Convert the given string to an integer by iterating through each digit, then check if it's divisible by 5 using modulo operator. This approach might cause overflow for very large numbers.

  • Initialize num = 0.
  • Traverse each character in string.
  • Update num = num × 10 + (digit).
  • Return true if num % 5 == 0 else false.
C++ 
#include <bits/stdc++.h>
using namespace std;

bool divisibleBy5(string &s)
{
    long long num = 0;

    // Convert the string into a number
    for (char ch : s)
    {
        num = num * 10 + (ch - '0');
    }

    // Check divisibility by 5
    return (num % 5 == 0);
}

int main()
{
    string s = "125";

    cout << divisibleBy5(s);

    return 0;
}
Java 
import java.util.*;

class GFG {
    static boolean divisibleBy5(String s) {
        long num = 0;

        // Convert the string into a number
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            num = num * 10 + (ch - '0');
        }

        // Check divisibility by 5
        return (num % 5 == 0);
    }

    public static void main(String[] args) {
        String s = "125";

        System.out.print(divisibleBy5(s));
    }
}
Python 
def divisibleBy5(s):
    num = 0

    # Convert the string into a number
    for ch in s:
        num = num * 10 + (ord(ch) - ord('0'))

    # Check divisibility by 5
    return (num % 5 == 0)


if __name__ == "__main__":
    s = "125"
    print(divisibleBy5(s))
C# 
using System;

class GFG {
    static bool divisibleBy5(string s) {
        long num = 0;

        // Convert the string into a number
        foreach (char ch in s) {
            num = num * 10 + (ch - '0');
        }

        // Check divisibility by 5
        return (num % 5 == 0);
    }

    static void Main(string[] args) {
        string s = "125";

        Console.Write(divisibleBy5(s));
    }
}
JavaScript 
function divisibleBy5(s) {
    let num = 0;

    // Convert the string into a number
    for (let i = 0; i < s.length; i++) {
        let ch = s[i];
        num = num * 10 + (ch.charCodeAt(0) - '0'.charCodeAt(0));
    }

    // Check divisibility by 5
    return (num % 5 === 0);
}

// Driver code
let s = "125";
console.log(divisibleBy5(s));

Output
1

[Optimal Approach] Last Digit Check - O(1) Time and O(1) Space

A number is divisible by 5 if and only if its last digit is 0 or 5. Since the number can be very large (given as string), directly check the last character instead of converting to integer.

  • Get last character of string using s.back().
  • Return 1 if last digit is '0' or '5'.
  • Return 0 otherwise.
C++ 
#include <bits/stdc++.h>
using namespace std;

int divisibleBy5(string &s)
{
    // Get the last digit of the number
    char lastDigit = s.back();

    // A number is divisible by 5
    // if its last digit is 0 or 5
    if (lastDigit == '0' || lastDigit == '5')
    {
        return 1;
    }

    return 0;
}

int main()
{
    string s = "125";

    cout << divisibleBy5(s);

    return 0;
}
Java 
import java.util.*;

class GFG {
    static boolean divisibleBy5(String s) {
        // Get the last digit of the number
        char lastDigit = s.charAt(s.length() - 1);

        // A number is divisible by 5
        // if its last digit is 0 or 5
        if (lastDigit == '0' || lastDigit == '5') {
            return true;
        }

        return false;
    }

    public static void main(String[] args) {
        String s = "125";

        System.out.print(divisibleBy5(s));
    }
}
Python 
def divisibleBy5(s):
    # Get the last digit of the number
    lastDigit = s[-1]

    # A number is divisible by 5
    # if its last digit is 0 or 5
    if lastDigit == '0' or lastDigit == '5':
        return True

    return False


if __name__ == "__main__":
    s = "125"
    print(divisibleBy5(s))
C# 
using System;

class GFG {
    static bool divisibleBy5(string s) {
        // Get the last digit of the number
        char lastDigit = s[s.Length - 1];

        // A number is divisible by 5
        // if its last digit is 0 or 5
        if (lastDigit == '0' || lastDigit == '5') {
            return true;
        }

        return false;
    }

    static void Main(string[] args) {
        string s = "125";

        Console.Write(divisibleBy5(s));
    }
}
JavaScript 
function divisibleBy5(s) {
    // Get the last digit of the number
    let lastDigit = s[s.length - 1];

    // A number is divisible by 5
    // if its last digit is 0 or 5
    if (lastDigit === '0' || lastDigit === '5') {
        return true;
    }

    return false;
}

// Driver code
let s = "125";
console.log(divisibleBy5(s));

Output
1
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