get digits:

reverse $ (rec \f (\v if (v = 0) [] (let r = divmod v 10 in (head (tail r)):(f (head r))))) 453532
=> [4 5 3 5 3 2]

pack digits:

foldl (\a \b a⋅10 + b) 0 [4 5 3 5 3 2]
=> 453532