Export ASP.Net GridView with Number format to Excel using C# and VB.Net

I have a gridview containing columns Payee Name, A/c No., IFS Code, Bank Name, PAN No., Amount.

Column Name A/c No. has values contaning more than 15 digits.

So after exporting this gridview column A/c No. replaces digits after 15 digit with 0.

e.g

Payee         A/c No.                    IFSC   Bank   PAN No.   Amount ABCD  98765432198765432198 XXXX   XXXX   XXXXXX    XXXXXX After Exporting

Payee         A/c No.                    IFSC   Bank   PAN No.   Amount ABCD  98765432198765400000 XXXX   XXXX   XXXXXX    XXXXXX Here 98765432198765432198 replaced with 98765432198765400000. Because of this problem I have to change miss matched account no. manually by checking each and every a/c no.

How to resolve this problem?

here is my code to export

        Response.Clear()
        Response.Buffer = True
        Response.ClearContent()
        Response.ClearHeaders()
        Response.Charset = ""
        Dim strwritter As New StringWriter()
        Dim htmltextwrtter As New HtmlTextWriter(strwritter)
        Response.Cache.SetCacheability(HttpCacheability.NoCache)
        Response.ContentType = "application/vnd.ms-excel"
        Dim FileName As String = "Payout Till" & a.ConvetDateToDDMMYY(Tdate) & ".xls"
        Response.AddHeader("Content-Disposition", Convert.ToString("attachment;filename=") & FileName)
        GridView1.GridLines = GridLines.Both
        GridView1.HeaderStyle.Font.Bold = True
        GridView1.RenderControl(htmltextwrtter)
        Response.Write(strwritter.ToString())
        Response.End()