piano chord
C13
C1E3G5B♭♭7D9A13
Seven notes in theory and four or five in anyone’s hands: root, third, seventh and thirteenth carry it.
What is true of it
C13 is C, E, G, B♭, D and A — 1, 3, 5, b7, 9 and 13 counted from C.
On an instrument that cannot reach all 6, the 5, 9 and 1 go first, in that order.