Base64 Decode : MjEyMw

Input : 
MjEyMw

Output: 
2123

Example code :

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

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

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

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