Application.unityVersion  

print ("Version of the runtime: " + Application.unityVersion);

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Awake() {
print("Version of the runtime: " + Application.unityVersion);
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Awake():
print(('Version of the runtime: ' + Application.unityVersion))