diff --git a/Prime_number.py b/Prime_number.py
index 1a345b5abe6..92800c63e83 100644
--- a/Prime_number.py
+++ b/Prime_number.py
@@ -23,7 +23,7 @@ def is_prime_b(n):
         if n == 2:
             return True
         else:
-            for i in range(2, n):
+            for i in range(2, int(n//2)+1):
                 if n % i == 0:
                     return False
             return True