c# Get numeric value of Enum

I have an Enum as follows:

public enum ApprovalStatus

{

    ReviewRequired = 657070000,

    Approved = 657070001,

    Rejected = 657070002

}

I have an function that passes in the literal value of this enum:

public void AddBillHeader(string org, ApprovalStatus approvalStatus)

        {

            IOrganizationService svc = GetXrmService(org);

            Entity bh = new Entity("fcbt_billheader");

            bh["fcbt_approvalstatus"] = //NEED THE NUMERIC VALUE OF THE ENUM HERE

            svc.Create(bh);

        }

To do that, I have to convert the value to an Int - simple as that:

(int)approvalStatus;