21^4
Some four letter words that have two vowels are:abetableacheacmeacneahemamenanteaveraxlebabebakebarebarebasebeadbeakbeambearbeatbeefbeenbeerbeetbidebikebiteblueboarboatboilbonebookbootboreboutbozobriecafecagecakecamecanecapecarecasecavecluecodecoedcoilcoincolacomacomeconecopecorecovecubecurecutedaledamedaredatadatedaubdazedeaddeafdealdeardeeddeemdeepdeerdelidemodialdicedimedinediredivadivedoledomedonedopedovedozedudedukedunedupeeachearlearneastechoecruedenedgeeditelseemiremitepicergoeveneverevilewerexamexitfacefadefailfairfakefamefarefatefaunfauxfazefearfeatfeedfeelfeetfetafetefeudfieffifefilefinefirefivefleafleefluefoalfoamfoilfootforefreefumefusegagagaingaitgalagalegamegapegategavegazegeargeargenegivegleegluegoadgoalgoalgoatgoesgonegoodgoofgoopgoregoutguruhailhairhalehaloharehatehaulhavehazeheadhealheaphearheatheedheelheirhereherohidehikehirehivehoaxhoboholehomehonehoodhoofhookhoophoothopehosehourhugehulaibexibisiconidleidolintoirisironisleitemjadejailjavajeerjivejoinjokejudojutekalekeelkeenkeepkenokilokitekiwikneekookkudolacelaidlainlairlakelamelanelatelaudlavalazeleadleafleakleanleapleekliarliceliedlienlifelikelimelimolinelionliveloadloafloamloanlobelocolodelogoloinlonelookloomloonlooplootlopeloreloseloudloutlovelubelugelureluteluxemacemademagimaidmailmaimmainmakemalemamamanemarematemaulmazemeadmealmeanmeatmeekmeetmemomenumeowmeremesametemicamicemikemilemimeminemiremitemoanmoatmodemoilmojomolemoodmoonmoormootmopemoremotemovemulemumumusemutenailnamenapenearneatneedneonniceninenodenoelnonenooknoonnopenosenotenounnovanudeoathodorogleogreoinkokraomenomitonceontooopsopalopenoralorcaorzoovaloveroxenpacepagepaidpailpainpairpalepanepapaparepatepavepeakpealpearpeatpeekpeelpeeppeerpeonpesopicapierpikepilepinepipepitapleapoempoetpokepoleponepopeporeposepucepukepumapurequadquayquidquipquitquizracerageraidrailrainrakeraperarerateraverazereadrealreamreaprearredoreedreefreekreelreinricerideriferilerimeriotriperiseriteroadroamroanroarroberoderoleroofrookroomrootroperoseroteroutroveruberuderuinrulerusesafesagasagesaidsailsakesalesamesanesarisavesealseamsearseatseedseekseemseenseepseershoesidesilosinesiresitesizesoaksoapsoarsodasofasoilsolesolosomesoonsootsoresoulsoupsourspuesuetsuitsuretabutacotailtaketaletametapetaretarotaxiteaktealteamtearteatteemteentheethoutidetiertiletimetinetiretoadtofutogatoiltometonetooktooltoottoretotetourtreetriotruetubatubetunatunetutuulnaundounituntouponurgeuservainvalevanevasevealveerveilveinvetovialviceviewvilevinevisavisevoidvolevotewadewadiwagewaifwailwaitwakewanewarewaveweakwealweanwearweedweekweepwerewheewhoawidewifewilewinewipewirewisewokewoodwoofwoolworewoveyeahyearyetiyogayokeyoreyouryulezealzerozetazitizonezoom
That is a trick question. You can't make a four letter word using all five vowels.
isle,else,also,
punt ugly
An eight letter word with three vowels using those letters is scavenge.Eight letter words with four vowels using those letters are agencies and envisage.
No. In the official Scrabble dictionary there are lots of four-letter words containing two i's, but no three-letter words.
fort
draw rawr
type eyes play yelp yolk
boeotian
Quid, quip, quad, aqua.
standardizing