Google search for «секси» comes up with 6,780,000 results, but «сексапильный» only comes up with 64,600. Is this trend also true in spoken Russian? Or are the results skewed for some reason (e.g. transliteration of titles of songs etc. from English)?

сексапильный - Google Search

секси - Google Search

(I was going to make a Google Fight to show this, but it seems it doesn't work for Cyrillic words unfortunately...)

Also as for indeclinable adjectives, I just thought of a couple of other ones... рок- as in рок-музыка, and онлайн. Are these slang too? Or can they only be used as prefixes?