The following function io[aIn\_] produces a list bOut containing ALL the prime factors of an Integer via the standard function FactorInteger[].
My code is:

```
io[aIn_] := 
(bOut = {};fi = FactorInteger[aIn];Do[bOut~AppendTo~(PadLeft[{}, fi[[i, 2]], fi[[i, 1]]] ), {i, 1, Length[fi]}]; bOut = bOut // Flatten )

```

I would like to know whether there are other solutions for this "problem"?

My solution does not work with e.g. aIn={12321}; io[aIn] nor with io[{12321}] or io[{12, 21}] and I do not understand all the warnings given by MMA.

I do not like to build a function that treats the integers of an input seperately and combines the results into a single list.  

I prefer a solution for io[] with "list in of composite integers" gives " list out of all prime factors".