Bb 13#11, 4th inversion (B# in the bass)
Also written as Bb13#11/B#.
Notes, from the bass up
B# (bass)EGA#DE#G#
The same notes as Bb 13#11 (B#, E, G, A#, D, E# and G#), rearranged so B# is the lowest note. Use it to move between chords with smaller jumps across the keyboard.