Please check the sentences and let me know your valuable feedback (My one friend said this to me and he meant to say "he is 24 years old" so I told him that "at" is unnecessary here, but he did not agree with me, so I just wanted to confirm this).
I think at is completely unnecessary here:
I am at 24 years old.
It should be:
1- I am 24.
2- I am 24 years old.