729/704, conventionally named the undecimal major diesis, is a medium comma measuring about 60.4 ¢. In Alpharabian tuning, it is called the Alpharabian infraaugmented prime or Alpharabian infraapotomic quartertone.
It is a type of quartertone that differs from 33/32 by 243/242, and is itself the interval left over after subtracting 33/32 from 2187/2048. While many may be accustomed to thinking of 33/32 and 729/704 as "semiaugmented primes", this analysis is only completely accurate when 243/242 is tempered out. This interval differs from the simpler 28/27 by the symbiotic comma.