The number of other permutations of the letters of the word SIMPLETON taken all at a time is 

The set of letters in the given word is $\left\{S,I,M,P,L,E,T,O,N\right\}$

There are 9 different letters. they can be arranged among themselves in $9!$ ways

Therefore, the number of other arrangments of letters of the word SIMPLETON taken at a time is $\boxed{9!-1}$