How to break an 18 digit number into parts

long subCode = Math.DivRem(num, 100, out num);
long ledcode = Math.DivRem(num, 10000, out num);
long curCode = Math.DivRem(num, 100, out num);
long cusCode = Math.DivRem(num, 10000000, out num);
long braCode = num;

class Program
{
  static readonly Regex TakeApart = new Regex("^(...)(.......)(..)(....)(..)$", RegexOptions.Compiled);
  static void Main(string[] args)
  {
    string num = "123456789123654258";
    Match m = TakeApart.Match(num);
    if (!m.Success)
    {
      // something went wrong!
    }
    string braCode = m.Groups[1].Value; //1st 3 digits
    string cusCode = m.Groups[2].Value; //from 4th to 10th digit
    string curCode = m.Groups[3].Value; //11th and 12th digit
    string ledcode = m.Groups[4].Value; //13th to 16th digit
    string subCode = m.Groups[5].Value; // 17th and 18th.
    // proceed ....
  }
}

try
            {
                long nNum = 123456789123654258;
                string sNum = nNum.ToString();

                int braCode = Int32.Parse(sNum.Substring(0, 3));    //123 //from 4th to 10th digit
                int cusCode = Int32.Parse(sNum.Substring(3, 7));    //4567891, from 4th to 10th digit
                int curCode = Int32.Parse(sNum.Substring(10, 2));   //23, //11th and 12th digit
                int ledcode = Int32.Parse(sNum.Substring(12, 4));   //6542, //13th to 16th digit
                int subCode = Int32.Parse(sNum.Substring(16, 2));   //58, // 17th and 18th.
            }
           catch(Exception ex)
            {
               // do smth!
            }

num=123456789123654258 //18 digit number
...
braCode=123, //1st 3 digit
cusCode=4567891, //from 4th to 10th digit
curCode=23, //11th and 12th digit
ledcode=6542, //13th to 16th digit
subCode=58, // 17th and 18th.

bracode = num.Substring(0,3)
subCode= num.Substring(16);

bracode = num.Substring(0,3)

cusCode = num.Substring(3,7)

subcode= num % 100
tmp= num / 100
ledcode= tmp % 10000
tmp= tmp / 10000
...