The number can be found in the database which is used to store hive meta data.
If MySql is the backend db,
select count(*) from TBLS;
What is the meaning of writing this?
Do you mean what is the use/need ? If so, for anyone who is a platform admin, if they would like to know how many hive tables are there in all the hive DBs put together, this query can help them answer. This was asked by a customer in one of the calls we had and thought it would help others with similar request. There is also a similar thread as this, feel free to refer this.