Prolog Term	Datatype IRI
float	xsd:double
integer	xsd:integer
string	xsd:string
true or false	xsd:boolean
date(Y,M,D)	xsd:date
date_time(Y,M,D,HH,MM,SS)	xsd:dateTime
date_time(Y,M,D,HH,MM,SS,TZ)	xsd:dateTime
month_day(M,D)	xsd:gMonthDay
year_month(Y,M)	xsd:gYearMonth
time(HH,MM,SS)	xsd:time

For example:

?- rdf_canonical_literal(42, X).
X = 42^^'http://www.w3.org/2001/XMLSchema#integer'.