As strange as it may seem, it's "aren't I"?
(You can say "Am I not?" but outside of certain regions, "amn't" -- although logical -- is not used.)

English Teacher
Which is the negative-interrogative contracted form of the verb TO BE in the first person singular? Is it Amn't I? it seems to me a little bit weird.
Contracted forms
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Aren’t you?
Isn’t he?
Isn’t she?
Isn’t it?
Aren’t we?
Aren’t you?
Aren’t they?
As strange as it may seem, it's "aren't I"?
(You can say "Am I not?" but outside of certain regions, "amn't" -- although logical -- is not used.)
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
***** NOT A TEACHER *****
Good afternoon, Mad-ox.
(1) I am sure that you already know this, but just in case that you do
not, may I respectfully call your attention to > ain't.
(2) This is considered uneducated speech. If a person uses this,
many other people will not respect that person's English.
(3) Of course, I have no proof, but I think that if a politician used this
word in most parts of the United States, s/he would not get elected.
(Although some politicians might say it on purpose to show that s/he is
one of the common people.)
(4) AIN'T:
I'm your best friend, ain't I?
He is your friend, ain't he?
We are going to the movies, ain't we?
(5) "Educated" people occasionally use it to be humorous: Ain't that the
truth!
Have a nice day!