[Range(1, int.MaxValue, ErrorMessage = "Value should be an integer")]
public int? LoanedTo { get; set; }

<div class="col-md-10">
    Loan Book To User (Id)
    <br />
    @Html.EditorFor(model => model.LoanedTo, new { htmlAttributes = new { @class = "form-control" } })
    @Html.ValidationMessageFor(model => model.LoanedTo, "", new { @class = "text-danger" })
</div>