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The 643 equal division divides the octave into 643 equal parts of 1.866 cents each. It is uniquely consistent to the 21-limit, with a generally flat tendency. It tempers out 32805/32768 in the 5-limit and 2401/2400 in the 7-limit, so that it supports sesquiquartififths temperament. In the 11-limit it tempers out 3025/3024 and | -1 3 -4 5 -2 >; in the 13-limit 1001/1000, 1716/1715 and 4225/4224; in the 17-limit 1089/1088, 1701/1700, 2431/2430 and 2601/2600; and in the 19-limit 1331/1330, 1521/1520, 1729/1728, 2376/2375 and 2926/2925. It provides the optimal patent val for the rank three 13-limit temperament vili temperament.