Ab 13sus4, 4th inversion (A# in the bass)
Also written as Ab13sus4/A#.
Notes, from the bass up
A# (bass)E#G#C#D#F#
The same notes as Ab 13sus4 (A#, E#, G#, C#, D# and F#), rearranged so A# is the lowest note. Use it to move between chords with smaller jumps across the keyboard.