[C#] Methods/ Task - 08 Big Number in Array

using System;
using System.Numerics;
class BigNumsInArray
{
    static int[] ReverseArray(int[] arr)
    {
        int[] reversed = new int[arr.Length];
        Array.Reverse(arr);
        for (int i = 0; i < arr.Length; i++)
            {
                reversed[i]=arr[i];
            }
        return reversed;
    }
    static BigInteger SumArrays(int[] arr1, int[] arr2)
    {
        BigInteger sum = 0;
        string num1="";
        string num2 = "";
        for (int i = 0; i < arr1.Length; i++)
        {
            num1 += arr1[i].ToString();
        }
        for (int i = 0; i < arr2.Length; i++)
        {
            num2 += arr2[i].ToString();
        }
        BigInteger first = BigInteger.Parse(num1);
        BigInteger second = BigInteger.Parse(num2);
        sum = first + second;
        return sum;
    }
    static void Main()
    {
        int[] firsArr = { 1, 6, 5, 9, 1, 5, 3, 2, 7 };
        int[] secondArr = { 4, 5, 7, 9, 4, 7, 1, 6, 2 };
        int[] reversedFirst = ReverseArray(firsArr);
        int[] reversedSecond = ReverseArray(secondArr);
        BigInteger sum = SumArrays(reversedFirst, reversedSecond);
        Console.WriteLine(sum);
    }
}