140/81, the septimal semidiminished seventh or septimal inframinor seventh is a 7-limit interseptimal ratio of about 947 cents. It is flat of a minor seventh 16/9 by a septimal quartertone 36/35, flat of a subminor seventh 7/4 by a syntonic comma 81/80, and sharp of a supermajor sixth 12/7 by a sensamagic comma 245/243.
It is also sharp of a major sixth 5/3 by a subminor second 28/27. For this fact it is useful in the Canovian chord and provides the function of a voice leading down to the major sixth. The canou temperament targets this progression and uses it as one of the generators.
The interval is so perfectly approximated by 19edo, with an error of 0.05 cents. There are a number of edos that do this equally well, 171edo to name one. The first edo that does this better than 19-edo with patent val is 660edo.