piano chord
E♭11
E♭1G3B♭5D♭♭7F9A♭11
Six notes in theory; in practice the third is usually dropped, because the eleventh sits a half step above it.
Written the other way round it is D♯11 — the same twelve keys on a piano, a different piece of notation.
What is true of it
E♭11 is E♭, G, B♭, D♭, F and A♭ — 1, 3, 5, b7, 9 and 11 counted from E♭.
On an instrument that cannot reach all 6, the 3, 5 and 1 go first, in that order.