Number or Charecter?

Hi,

I have a Varchar2 column for the telephone numbers.
Sometimes we get the telephone numbers with charecters.
Is there a way to find out those telephone numbers with charecters?
The table contains 4 million rows.
my oracle version is 8.1.7.4 running in Win2000 adv server.
Thanks for your help
Dan

select * from phone_numbers_table
where translate(phone_number_column,'a0123456789','a') is not null;

Thanks very much.
It works great
Dan