ת Tav - 22nd letter, Gematria 400
ת is pronounced, both in Modern Hebrew and Aramaic, as T found in Romance languages or as English T (but less "breathy").
ת is not only the last letter of the AlefBet, but also the last letter in BegadKephat group of letters that may have a secondary pronunciation, depending on what other sound proceeds them. In Aramaic, for ת, the secondary pronunciation is like TH in Thick or Thistle. In Modern Hebrew, ת is always pronounced as T only.
Translated from Greek, Jesus says "I am Alpha and Omega".
Supposing that Jesus spoke to John in Hebrew and then that was translated into Greek, then He would have said:
"אני האלף והתו" (Ani ha'Aleph vehaTav) - I am the Alef and the Tav.
Now if He spoke in Aramaic (which was the commonly spoken language in Israel at the time), He would have said something like:
אנא אלף ואנא תו (Ana alap we'ana taw) - I am Alap and I am Taw.