I don't know the total number, but some examples are below:
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There are many, but here are some examples:bagelbastebatchbathecabincachecamelcatchcaterdaddydailydairydaisydandyeagerearnseartheaselfablefacetfaintfaithfavorgablegaudygaugegaunthabithaikuharshhaunthavenjadedjauntjazzykaputkarmakayakkazoolabellaborladenlatchlatermacawmachomajormarchmarshmasonmatchnachonaivenakednannynastynavelpaganpagerpaperparchpastepatchpavedradarrabbirabidradioradonranchrazorsabersablesaintsaladsatinsavedsavortabletabootacittallytangotardytarryvaguevalidvalorvaluevalvevaporwagerwaferwaivewastewatchwaterwavedyachtyards
Thousands of words contain the letter L. Words that begin with L include labor, lad, lamp, last, lawn, leg, letter, lion, locomotive, lollipop, lost, love and luck.
Far too many to list: true, blue, bub, accrue, acetous, curious, infamous are a few. Use a crossword solver to find more (see links below).
THere are 303 words that begin with the letter X.
Just one - Mississippi. I checked the Scrabble dictionary and Webster's Second International dictionary (around 250,000 words in each).