Data update

Task/Additive-primes/C-sharp/additive-primes.cs

@@ -0,0 +1,86 @@
+internal class Program
+{
+    private static void Main(string[] args)
+    {
+        long primeCandidate = 1;
+        long additivePrimeCount = 0;
+        Console.WriteLine("Additive Primes");
+
+        while (primeCandidate < 500)
+        {
+            if (IsAdditivePrime(primeCandidate))
+            {
+                additivePrimeCount++;
+
+                Console.Write($"{primeCandidate,-3} ");
+
+                if (additivePrimeCount % 10 == 0)
+                {
+                    Console.WriteLine();
+                }
+            }
+
+            primeCandidate++;
+        }
+
+        Console.WriteLine();
+        Console.WriteLine($"Found {additivePrimeCount} additive primes less than 500");
+    }
+
+    private static bool IsAdditivePrime(long number)
+    {
+        if (IsPrime(number) && IsPrime(DigitSum(number)))
+        {
+            return true;
+        }
+
+        return false;
+    }
+
+    private static bool IsPrime(long number)
+    {
+        if (number < 2)
+        {
+            return false;
+        }
+
+        if (number % 2 == 0)
+        {
+            return number == 2;
+        }
+
+        if (number % 3 == 0)
+        {
+            return number == 3;
+        }
+
+        int delta = 2;
+        long k = 5;
+
+        while (k * k <= number)
+        {
+            if (number % k == 0)
+            {
+                return false;
+            }
+
+            k += delta;
+            delta = 6 - delta;
+        }
+
+        return true;
+    }
+
+    private static long DigitSum(long n)
+    {
+        long sum = 0;
+
+        while (n > 0)
+        {
+            sum += n % 10;
+            n /= 10;
+        }
+
+        return sum;
+    }
+}