Answer:
There are 22 letters in the Hebrew alphabet.
This does not include the 5 letters that are written differently if they appear at the end of a word (ך ם ן ץ ף), or the "dotted versions" of several pairs of letters that have 2 pronunciations and use dots to distinguish them (בּב, גּג, דּד, ווּוֹ, כּכ, פּפ, שׁשׂ, תּת).