P.Oxy LXVI 4499
It's there on the third line, chi, iota, stigma (hexakosiai deka hex).
For a useful video introduction to the issues, see my post from yesterday, Number of the Beast: 666 or 616: how does it work?, which features Ian Boxall and David Parker.
For an earlier post on the topic here, see The Number of the Beast: 616 and Oxyrhynchus.
Relevant bibliography includes:
David C. Parker, "A New Oxyrhynchus Papyrus of Revelation: P115 (P.Oxy 4499)", NTS 46 (2000): 159-74
Peter M. Head, "Some Recently Published NT Papyri from Oxyrhynchus: An Overview and Preliminary Assessment", Tyndale Bulletin 51 (2000): 1-16 [Available online in PDF format - click article title]
I may add a bit more here in due course.