extract and interval

Is there an good way to extract the interval unit that were used?

E.g. I used interval '2h' and another case I used '3d', theses are
respectively 2 hours and 3 days, but the format that came on select is
'02:00:00' for hour and '3 days' for days

What I'm looking for is something like 2h and 3d just as inserted.
The only solution so far I could came up with is call to_char function using
the unit of time and get the highest position for each couple of digits.
Ex: to_char(interval, 'DDHH24')
let's suppose the result is 0003 then I know it's 3 hours if I get 0100 I
know it's 1 day.

Open to suggestions :)