You are getting this error because the value cannot be found in the range. String or integer doesn't matter. Best thing to do in my experience is to do a check first to see if the value exists.
I used CountIf below, but there is lots of different ways to check existence of a value in a range.
Public Sub test()
Dim rng As Range
Dim aNumber As Long
aNumber = 666
Set rng = Sheet5.Range("B16:B615")
If Application.WorksheetFunction.CountIf(rng, aNumber) > 0 Then
rowNum = Application.WorksheetFunction.Match(aNumber, rng, 0)
Else
MsgBox aNumber & " does not exist in range " & rng.Address
End If
End Sub
ALTERNATIVE WAY
Public Sub test()
Dim rng As Range
Dim aNumber As Variant
Dim rowNum As Long
aNumber = "2gg"
Set rng = Sheet5.Range("B1:B20")
If Not IsError(Application.Match(aNumber, rng, 0)) Then
rowNum = Application.Match(aNumber, rng, 0)
MsgBox rowNum
Else
MsgBox "error"
End If
End Sub
OR
Public Sub test()
Dim rng As Range
Dim aNumber As Variant
Dim rowNum As Variant
aNumber = "2gg"
Set rng = Sheet5.Range("B1:B20")
rowNum = Application.Match(aNumber, rng, 0)
If Not IsError(rowNum) Then
MsgBox rowNum
Else
MsgBox "error"
End If
End Sub