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_name_11 (number_of_mobile_phones VARCHAR, last_updated_date VARCHAR)

### Question ###
How many mobile phones were there as of April 2013?

### Accurate SQL ###

SELECT number_of_mobile_phones FROM table_name_11 WHERE last_updated_date = "april 2013"