diff --git a/challenges/defibrillators/solutions/python/function/solution.py b/challenges/defibrillators/solutions/python/function/solution.py
index 78a4d96..189cc58 100644
--- a/challenges/defibrillators/solutions/python/function/solution.py
+++ b/challenges/defibrillators/solutions/python/function/solution.py
@@ -13,8 +13,8 @@ def convert_string_to_float(string: str) -> float:
 
 class Position:
     def __init__(self, longitude: float, latitude: float) -> None:
-        self.longitude = self.convert_degrees_to_radien(longitude)
-        self.latitude = self.convert_degrees_to_radien(latitude)
+        self.longitude = self.convert_degrees_to_radian(longitude)
+        self.latitude = self.convert_degrees_to_radian(latitude)
 
     @staticmethod
     def calculation_distance(pointA: 'Position', pointB: 'Position') -> float:
@@ -23,7 +23,7 @@ class Position:
         y = pointB.latitude - pointA.latitude
         return math.sqrt(math.pow(x, 2) + math.pow(y, 2)) * 6371
 
-    def convert_degrees_to_radien(self, degrees: float) -> float:
+    def convert_degrees_to_radian(self, degrees: float) -> float:
         return degrees * (math.pi / 180)
 
 
diff --git a/challenges/first-non-repeating-character/README.md b/challenges/first-non-repeating-character/README.md
index f5969a3..46fad70 100644
--- a/challenges/first-non-repeating-character/README.md
+++ b/challenges/first-non-repeating-character/README.md
@@ -6,7 +6,7 @@ Created by [@Divlo](https://github.com/Divlo) on 15 November 2020.
 
 Write a function that takes a string input, and returns the first character that is not repeated anywhere in the string.
 
-For example, if given the input `'stress'`, the function should return `'t'`, since the letter _t_ only occurs once in the string, and occurs first in the string.
+For example, if given the input `'stress'`, the function should return `'t'`, since the letter `'t'` only occurs once in the string, and occurs first in the string.
 
 If a string contains all repeating characters, it should return an empty string (`""`).
 
diff --git a/challenges/is-prime-number/solutions/cs/function/README.md b/challenges/is-prime-number/solutions/cs/function/README.md
new file mode 100644
index 0000000..2e099fc
--- /dev/null
+++ b/challenges/is-prime-number/solutions/cs/function/README.md
@@ -0,0 +1,3 @@
+# is-prime-number/cs/function
+
+Created by [@Divlo](https://github.com/Divlo) on 10 September 2021.
diff --git a/challenges/is-prime-number/solutions/cs/function/Solution.cs b/challenges/is-prime-number/solutions/cs/function/Solution.cs
new file mode 100644
index 0000000..f86d576
--- /dev/null
+++ b/challenges/is-prime-number/solutions/cs/function/Solution.cs
@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+
+namespace Solution
+{
+    class Program
+    {
+        static void Main()
+        {
+            int number = int.Parse(Console.ReadLine());
+            if (IsPrime(number))
+            {
+                Console.WriteLine("true");
+            }
+            else
+            {
+                Console.WriteLine("false");
+            }
+        }
+
+        /// <summary>
+        /// Checks if a number is prime.
+        /// </summary>
+        /// <param name="number">The number to check.</param>
+        /// <returns>True if the number is prime, false otherwise.</returns>
+        static public bool IsPrime(int number)
+        {
+            return GetDividers(number).Length == 2;
+        }
+
+        /// <summary>
+        /// Gets the dividers of a number.
+        /// </summary>
+        /// <param name="number">The number to get the dividers of.</param>
+        /// <returns>An array of the dividers of the number.</returns>
+        static public int[] GetDividers(int number)
+        {
+            List<int> dividers = new List<int>();
+            for (int index = 1; index <= number; index++)
+            {
+                if (number % index == 0)
+                {
+                    dividers.Add(index);
+                }
+            }
+            return dividers.ToArray();
+        }
+    }
+}