Error In Converting Datatype Nvarchar To Bigint?

this code is giving me error:

error in converting datatype nvarchar to bigint this is my table values:

@customer_first_name nvarchar(50),
@customer_last_name nvarchar(50),
@customer_address nvarchar(max),
@gender nchar(10),
@date_of_birth datetime,
@customer_email_id varchar(50),
@customer_occuption varchar(50),
@customer_phone_number Bigint,
@nominee_name nchar(50),
@customer_id nvarchar(50),
@account_type nvarchar(50),
@account_number nvarchar(50),
@transfer_access_code nvarchar(50),
@account_balance Bigint,
@pin_code BigInt,
@nationality nvarchar(50),
@password nvarchar(50)
lblAmount.Text = HFamount .Value ;
int balamount = Convert.ToInt32(lblAmount.Text);
int Cpincode = Convert.ToInt32(txtpincode.Text);
long phone = Convert.ToInt64(txtphone.Text);
string cust_id = CUSTOMER_ID_GENERATOR();
string strconstring = ConfigurationManager.ConnectionStrings["ONLINE_BANKING2_ConnectionString"].ConnectionString;
SqlConnection mycon = new SqlConnection(strconstring);
mycon.Open();
SqlCommand cmdRegister= new SqlCommand(sqlquery,mycon);
cmdRegister.Parameters.Add(new SqlParameter("@customer_first_name",txtcustname.Text.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@customer_last_name",txtcustlastname.Text.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@customer_address",txtAddress.Text.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@gender", rbtngender.SelectedItem.Value.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@date_of_birth", txtDOB.Text));
cmdRegister.Parameters.Add(new SqlParameter("@customer_email_id", txtemail.Text.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@customer_occuption", txtcustoccupation.Text.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@customer_phone_number", phone));
cmdRegister.Parameters.Add(new SqlParameter("@nominee_name", txtnominee.Text.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@customer_id", cust_id));
cmdRegister.Parameters.Add(new SqlParameter("@account_type", accType.SelectedItem.Value.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@account_number", ACCOUNT_NUMBER_GENERATOR()));
cmdRegister.Parameters.Add(new SqlParameter("@transfer_access_code",Transfer_code()));
cmdRegister.Parameters.Add(new SqlParameter("@account_balance", balamount));
cmdRegister.Parameters.Add(new SqlParameter("@pin_code", Cpincode));
cmdRegister.Parameters.Add(new SqlParameter("@nationality", DropCountry.SelectedItem.Value.ToString()));
cmdRegister.Parameters.Add(new SqlParameter("@password",txtpasswd2.Text.ToString()));
cmdRegister.ExecuteNonQuery();
mycon.Close();