diff --git a/maths/armstrong_numbers.py b/maths/armstrong_numbers.py
index d30ed2e43..af25688db 100644
--- a/maths/armstrong_numbers.py
+++ b/maths/armstrong_numbers.py
@@ -1,5 +1,6 @@
 """
-An Armstrong number is equal to the sum of the cubes of its digits.
+An Armstrong number is equal to the sum of its own digits each raised
+to the power of the number of digits.
 For example, 370 is an Armstrong number because 3*3*3 + 7*7*7 + 0*0*0 = 370.
 An Armstrong number is often called Narcissistic number.
 """