Add Factorial in kotlin

code/mathematical_algorithms/src/factorial/Factorial.kt

@@ -0,0 +1,28 @@
+package csd.gisc.hacktoberfest2018
+
+import java.math.BigInteger
+import java.util.*
+
+/**
+ * Created by Phuwarin on 10/4/2018
+ * Part of Cosmos by OpenGenus
+ */
+
+object Factorial {
+
+    @JvmStatic
+    fun main(args: Array<String>) {
+        print("Enter a number: ")
+        val enterNum = Scanner(System.`in`)
+        val n = enterNum.nextLong()
+        println("Factorial is: " + factorial(n))
+    }
+
+    private fun factorial(n: Long): BigInteger {
+        var result = BigInteger.ONE
+        for (i in 1..n) {
+            result = result.multiply(BigInteger.valueOf(i))
+        }
+        return result
+    }
+}