In the Sumerian King List, King Alulim is said to have ruled Eridu for 28,800 years.
Alulim is presented as the first king in the list’s antediluvian section, and Eridu is given as the first city to receive kingship. The enormous reign length belongs to the legendary chronology of the text, not to a conventional historical dating system.
The King List combines mythic rulers, legendary figures, and historically attested dynasties. Its purpose appears to include presenting kingship as a transferable institution that moved from city to city, rather than providing a modern-style continuous history.
The extreme numbers are a defining feature of the antediluvian section. Later rulers have much shorter reigns, especially after the flood, although some early figures still receive unusually long totals.