VBA - function Vlookup

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Hi everyone,
In my module i pretend search a value corresponding to a variable a.
But when i run the code variable h are incorrect, because apeear error 2042 and the suppose is appear a number.

My code is:

Sub Macro3()
    Dim j As Variant
    Dim a As Variant
    Dim h As Variant 'variavel de teste
    Set Model = Workbooks("AtrasosTotal.xlsm").Worksheets("Model")
    lastRowZModel = Model.Cells(Model.Rows.Count, "A").End(xlUp).Row
    a = 1600104092
    Sheets("Model").Select
    Set b = Range("A2:O" & lastRowZModel)
    h = Application.VLookup(a, b, 12, False)
End Sub

How can I resolve this problem