I wonder why the Sumerians deviated on the last two lengths from the rule they had on the first six. The first six reign lengths (and the total sum of all eight reign lengths) are all n * 60 * 60, where n is an integer. The last two are not, but they could’ve been. If instead you use 18000 years and 21600 years instead of 18600 and 21000, they fit the same formula as the other numbers and the sum remains the same. They used base 60, and apparently got a kick out of multiplying 60 by itself and another integer.

I noticed the deviation because there are mechanical watch movements that run at 18000 and 21600 beats per hour.