Like when we say un-happi-ness (prefix, root, and suffix), how can we divide withdrawal?
-al is certainly a suffix, but whether you regard with- as a prefix, or withdraw as an unanalysable word is a matter of choice, depending partly on your timescale.
Historically, certainly withdraw derives from prefix with- and root draw. With- is also found in withhold and withstand, and meant "against". But it is not a productive prefix in modern English, and its meaning is not obvious in withdraw, so I suspect that most people's mental lexicon does not list withdraw as a prefixed word.
According to Etymology Online Dictionary: withdraw (v.) early 13c. (transitive), "to take back," from with "away" + drawen "to draw. So: With - prefix. Draw - root.
withdrawal (n.) 1820s, "act of taking back," also "retraction of a statement," from withdraw + -al. So: -al - suffix.