piano chord
D♭11
D♭1F3A♭5C♭♭7E♭9G♭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 C♯11 — the same twelve keys on a piano, a different piece of notation.
What is true of it
D♭11 is D♭, F, A♭, C♭, E♭ and G♭ — 1, 3, 5, b7, 9 and 11 counted from D♭.
On an instrument that cannot reach all 6, the 3, 5 and 1 go first, in that order.