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File with weird permissions, impossible to delete

I have some files, with weird permissions:

# ls -la
d-wS--S--T 2 1061270772 2605320832  4096 oct.   7  2412 index.html

Cannot delete, cannot change owner or group (what is this user
1061270772 and group 2605320832 by the way?) even for root.

How can I get rid of these?