Pulling Out The Numbers

I've been looking around for this all day. Is there anyway to determine if a non number variable can be converted cleanly to a number? In other words the equivalent to an IsNumber function in Oracle.

I have some garbage data that I'm attempting to clean up and I'd like to pull the numeric data from a column and put the data that is alphanumeric into a comment column.

Thanks.

Code:

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CREATE OR REPLACE FUNCTION IsNumber (p_in VARCHAR2)
RETURN VARCHAR2 IS
  dummy NUMBER;
BEGIN
  dummy := p_in;
  RETURN 'True';
EXCEPTION
  WHEN OTHERS THEN RETURN 'False';
END;
/

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