Reply to comment:

Mirjam Kühne
Hi Jaris. Sorry for the delay. We looked at our Routing Information Service (RIS) and found that currently 4,712 /32s are seen by at least 10 RIS peers. In total they see 11,422 IPv6 prefixes. You can also look at the RIS output yourself: http://www.ris.ripe.net/dumps/riswhoisdump.IPv6.gz