Base64 Encode : 4150

Input : 
4150

Output: 
NDE1MA==

Example code :

Code PHP - base64_decode():
<?php
  $str = '4150';
  echo base64_decode($str);
?>

Code Python - base64.b64decode() :
<<< import base64
<<< encoded = '4150'
<<< data = base64.b64decode(encoded)
<<< data

Code JavaScript - atob() :
atob('4150');

Code C# - System.Convert.FromBase64String() : 
string base64Encoded = "4150";
byte[] data = System.Convert.FromBase64String(base64Encoded);
string base64Decoded = System.Text.ASCIIEncoding.ASCII.GetString(data);