Hyphen usage

hxq2007

I have been unable to get a clear idea of whether or not the use of a
hyphen is still Required Usage when making compound adjectives
containing numerals. They seem to be required in something like \"a
twelve-storey building\", but what about \"a 12 storey building\", or \"a
six-sided dice\" versus \"a 6-sided dice\" or \"a 6 sided dice\"?

The specific usage that raises the question is in a book catalogue
where we have expressions such as \"this 310-page book\". One editor
wants to insert the hyphens and t'other reckons they look wrong.

Comments?