Issue in comparing result_value to constant.

Hello

I have a requirement to display values(hours) from the  pay_run_result_values where the value is over a certain amount. When I run this query, I get an "invalid number" error. I'm accounting for null values and since I'm restricting the query to return hours I should have any non-numeric data either. Any pointers?

select  piv.input_value_id, to_number(nvl(pay_prrv1.result_value,0))

     from   pay_run_result_values pay_prrv1,     pay_input_values_f piv

       where piv.name              = 'Hours'

        and to_number(nvl(pay_prrv1.result_value,0)) >= 2

          and piv.input_value_id    = pay_prrv1.input_value_id