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_3648 ( "Country or territory with flag" text, "Area (km\u00b2) (per sqmi)" text, "Population (July 2009 est.)" real, "Population density per km\u00b2" text, "Capital" text )

### Question ###
What is the capital of the country with a population density per km of 15.6/km (/sqmi)?

### Accurate SQL ###

SELECT "Capital" FROM table_3648 WHERE "Population density per km\u00b2" = '15.6/km² (/sqmi)'