This is pretty easy if you understood that we live in a world of base 10 and the principles of division with rest:
n = 781049;
Rest@Reverse[Flatten@Last@Reap@FixedPointList[(Sow[Mod[#, 10]]; Quotient[#, 10]) &, n]]
(* {7, 8, 1, 0, 4, 9} *)
or as J.M. suggested with one call to get the quotient and the remainder
With[{n = 781049}, Reverse[Reap[NestList[Block[{q, r},
{q, r} = QuotientRemainder[#, 10]; Sow[r]; q] &, n, IntegerLength[n]]][[-1, 1]]]]
If you really prefer shorter methods, than you could go with
IntegerDigits[n]
or maybe
ToExpression@StringCases[ToString[n], DigitCharacter]
if you like strings.