Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_19706 ( "Prefix size" text, "Network mask" text, "Available subnets" real, "Usable hosts per subnet" real, "Total usable hosts" real )

### Question ###
When the network mask is 255.255.255.224 what is the highest total usable host?

### Accurate SQL ###

SELECT MAX("Total usable hosts") FROM table_19706 WHERE "Network mask" = '255.255.255.224'