piano chord
A♯7
A♯1C𝄪3E♯5G♯♭7
Major triad, minor seventh. The chord that wants to resolve a fourth up.
Written the other way round it is B♭7 — the same twelve keys on a piano, a different piece of notation.
What is true of it
A♯7 is A♯, C𝄪, E♯ and G♯ — 1, 3, 5 and b7 counted from A♯.
C𝄪 is a double sharp, and it has to be: every letter from A♯ upwards is used once, so the 3 cannot be written any other way.
On an instrument that cannot reach all 4, the 5 goes first, in that order.