Usually we use "Cinquecento"/"Settecento"/"Novecento" to refer to the 1500s, 1700s and 1900s (even if it sounds like 500, 700 and 900). It is the most common use and it might sound a bit confusing, but if you clarify the context, people can easily understand if you are talking about the 6th century or the 16th century.
In English there is a similar concept: it's like saying "the '50s", "the '70s" and "the '90s" to refer to 1950s, 1970s and 1990s. Of course these decades don't only exist in the 1900s, but it's the most common use.