As the others pointed out, 21C is too low. Hedgehogs need 72F at minimum, but they often prefer it a few degrees warmer. 21C is under 70F, which can risk a hibernation attempt, and being too cold or being in the beginnings of a hibernation attempt can definitely cause grumpiness and low activity. 23-25C is what to aim for.
Could definitely be quilling in addition to the temperature, as some hedgehogs will have an "attitude problem" from quilling that goes even to 15-16 weeks old before tapering off. You should handle him as much as possible despite the grump. Invest in a sleeping/cuddle bag so you can have him out on your lap - a carry bag is also excellent for socialization and bonding, so you can carry him around the house while you do other things. Also remember that hedgehogs in general tend to be timid and defensive by nature, and a lot of hedgies will have at least a little bit of a "grumpy streak" their entire lives. It's just part of their personality. While it can be frustrating for a new owner to have to deal with the initial quilling period, especially if it's a very bad quilling, part of owning a hedgehog is understanding that they might never be a perfectly friendly, outgoing, or cuddly pet. Try to be patient and love him for what he is, even if he doesn't turn out exactly how you hoped.