POiSON WORLD

CREATE FUNCTION numToEasternArabic(
  in_value IN NUMBER
) RETURN NVARCHAR2 DETERMINISTIC
IS
  p_num  VARCHAR2(100) := TO_CHAR( in_value );
  p_char CHAR(1);
  o_str  NVARCHAR2(100);
BEGIN
  FOR i IN 1 .. LENGTH( p_num ) LOOP
    p_char := SUBSTR( p_num, i, 1 );
    o_str := o_str
          || CASE p_char
             WHEN '.'
             THEN N'.'
             ELSE UNISTR(
                    '\' || TO_CHAR(
                             TO_NUMBER( p_char ) + 660,
                             'FM0000'
                           )
                  )
             END;
  END LOOP;
  RETURN o_str;
END;
/

Query 1:

SELECT numToEasternArabic( 1438 )
FROM   DUAL

Results:

| NUMTOEASTERNARABIC(1438) |
|--------------------------|
|                     ١٤٣٨ |