From Halopedia, the Halo wiki
07-117649 was a monitor and the caretaker of Installation 07. After the United Nations Space Command established a presence on Installation 07 in 2555, around three hundred researchers were contracted by the Office of Naval Intelligence to study the ring as part of the Zeta Halo project. However, monitor 117649 had not yet been discovered by any research detachment. Doctor Luther Mann theorized that it was possible that the monitor had heard about humanity's and the Covenant's presence on other installations—which led to the destruction of Installation 04, the partial glassing of Installation 05, and the destruction of Installation 04's replacement—and decided to remain hidden from the researchers.
Following in line with the pattern of exponential numbers of base 7 as the names for the Halo's monitors, 117649 is equal to 7 raised to 6th power.
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