Do such numbers relate to quality? (5)
I believe the answer is:
prime
'to quality?' is the definition.
('prime' can be a synonym of 'quality')
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for prime that I've seen before include "Monastic service; best quality" , "(Of number) divisible only by itself and one" , "Of first quality" , "Capital - of first importance" , "Prepare to fire - first" .)