F11

F1A3C5E♭♭7G9B♭11

Six notes in theory; in practice the third is usually dropped, because the eleventh sits a half step above it.

What is true of it

F11 is F, A, C, E♭, G and B♭ — 1, 3, 5, b7, 9 and 11 counted from F.

On an instrument that cannot reach all 6, the 3, 5 and 1 go first, in that order.