mandatory vs compulsory

mandatory is a noun but compulsory is not a noun.

Word	Noun	Adjective	Verb	Adverb
mandatory	Yes	Yes	No	No
compulsory	No	Yes	No	No

As adjectives, mandatory and compulsory are synonyms defined as:

Other synonyms of mandatory include required.

mandatory (noun)	compulsory (noun)
a territory surrendered by Turkey or Germany after World War I and put under the tutelage of some other European power until they are able to stand by themselves
the recipient of a mandate

mandatory (adjective)	compulsory (adjective)
required by rule	required by rule