diff --git a/src/Python/Problems001-050/Problem021.py b/src/Python/Problems001-050/Problem021.py
index 1ea1f43..732d184 100644
--- a/src/Python/Problems001-050/Problem021.py
+++ b/src/Python/Problems001-050/Problem021.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/env python
 """
 Created on 15 Sep 2018
 
@@ -11,24 +11,27 @@ https://projecteuler.net/problem=21
 
 from utils import timeit
 
+
 def sum_divisors(n):
-    return sum(i for i in range(1, n//2+1) if n%i==0)
+    return sum(i for i in range(1, n // 2 + 1) if n % i == 0)
+
 
 @timeit("Problem 21")
 def compute():
     """
-    Let d(n) be defined as the sum of proper divisors of n (numbers 
+    Let d(n) be defined as the sum of proper divisors of n (numbers
     less than n which divide evenly into n).
     If d(a) = b and d(b) = a, where a ≠ b, then a and b are an amicable
     pair and each of a and b are called amicable numbers.
 
-    For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 
-    44, 55 and 110; therefore d(220) = 284. The proper divisors of 284 are 
+    For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22,
+    44, 55 and 110; therefore d(220) = 284. The proper divisors of 284 are
     1, 2, 4, 71 and 142; so d(284) = 220.
 
     Evaluate the sum of all the amicable numbers under 10000.
     """
-    n = 10000
+
+    n = 10_000
     sum_amicable = 0
     for i in range(1, n):
         value = sum_divisors(i)
@@ -38,5 +41,4 @@ def compute():
 
 
 if __name__ == "__main__":
-
-    print(f"Result for Problem 21: {compute()}")
\ No newline at end of file
+    print(f"Result for Problem 21 is {compute()}")