Can I use filteredtextbx extender from ajax control toolkit of html input?

i want to allow only numbers to be entered in an input field. HTML is pasted below. I get the following error. Please help. Thanks

Extender control 'FilteredTextBoxExtender1' cannot extend 'txtCardNumber'. Extender controls of type 'AjaxControlToolkit.FilteredTextBoxExtender' cannot extend controls of type 'System.Web.UI.HtmlControls.HtmlInputText'

 <input id="txtCardNumber" autofocus  runat="server" type="text"
                class="form-control focus" placeholder="Password" maxlength="127" />
            <asp:RequiredFieldValidator ID="RequiredFieldValidator4" runat="server"
                SetFocusOnError="true" ControlToValidate="txtCardNumber" Text="• Card number is required" ForeColor="Red" Display="Static"></asp:RequiredFieldValidator>
                    <asp:FilteredTextBoxExtender ID="FilteredTextBoxExtender1"
                                            runat="server" ClientIDMode="Predictable" Enabled="True" FilterType="Numbers"
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Naitik GamitSoftware DeveloperCommented:
Use TargetControlID="RequiredFieldValidator4" in FilteredTextBoxExtender


<asp:FilteredTextBoxExtender ID="FilteredTextBoxExtender1"
                                             runat="server" ClientIDMode="Predictable" Enabled="True" FilterType="Numbers"

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