How many {armament} are for {MiG-21} ?
MiG-21 has how many armaments?
How many armaments does the MiG-21 have?
SELECT ( COUNT ( ?y ) AS ?v ) { resource:MiG-21 property:armament ?y }
SELECT (COUNT(?obj) AS ?objs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q150609> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P520> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
} 

SELECT (COUNT(?obj) AS ?value ) { wd:Q150609 wdt:P520 ?obj }
6