piano chord
A♭13
A♭1C3E♭5G♭♭7B♭9F13
Seven notes in theory and four or five in anyone’s hands: root, third, seventh and thirteenth carry it.
Written the other way round it is G♯13 — the same twelve keys on a piano, a different piece of notation.
What is true of it
A♭13 is A♭, C, E♭, G♭, B♭ and F — 1, 3, 5, b7, 9 and 13 counted from A♭.
On an instrument that cannot reach all 6, the 5, 9 and 1 go first, in that order.