Six is mostly arithmetic here
Searching Mesopotamian myth for a mystical “number 6” turns up very little. The weight that six carries in the region is mainly mathematical: it is one of the two alternating factors that built the base-60 counting system used by the Sumerians and later the Babylonians. Where numbers do enter religion, it is usually through sixty, not six. This article follows the documented evidence and leaves later mystical readings aside.
How the system worked
Most of the world counts in tens. Early Mesopotamian scribes used a system in which the unit steps alternate between ten and six. Reading the Sumerian number words and signs, the sequence runs roughly 1, 10, 60, 600, 3,600 and 36,000: ten times one is ten, six times ten is sixty, ten times sixty is 600, six times 600 is 3,600, and so on. That alternation is why the Mesopotamian sexagesimal system is described as having both a base of 60 and a sub-base of 10.
In the Old Babylonian period, roughly 2000 to 1600 BCE, scribes turned this into a true place-value notation, in which the same wedge-shaped sign could mean 1, 60, 3,600 or a fraction depending on its position. Two basic signs, a vertical wedge for one and a corner wedge for ten, were enough to write every digit from 1 to 59. This cuneiform place value notation is one of the earliest known positional systems. Early tablets often left a gap where a position was empty. A dedicated empty-place marker sign came into use later, in the last centuries BCE, and it served as a separator and not as a number in the modern sense.
Why sixty?
Nobody can say for certain why the Mesopotamians settled on 60, and the sources do not record a reason. Several explanations are suggested by modern scholars.
- Many divisors. Sixty divides evenly by 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30 and 60. That makes halves, thirds, quarters, fifths and sixths of a quantity easy to express, which suits trade and land measurement.
- Merged systems. One proposal is that two earlier counting habits, one based on ten and one on six or twelve, were combined by scribes.
- Finger-joint counting. Another suggestion is that people counted the twelve finger joints of one hand with the thumb, and tracked each dozen on the five fingers of the other, giving 12 times 5, which is 60. This is an appealing picture, but it is a hypothesis, and similar methods are known mainly from later and distant regions.
None of these is proven. What is clear is that a system rich in divisors was convenient for calculation, and that once such a system was embedded in schools and administration it tended to stay.
Sixty in religion and ritual
The clearest link between sixty and the divine comes from later god lists, in which deities were given numbers according to their rank. Anu, the sky god and head of the hierarchy, is associated with 60. Enlil is given 50, Ea 40, and the moon god Sin 30, with other gods following lower numbers. These assignments are attested in scholarly texts, though lists vary in detail. They show scribes treating the top of their number system as the number of the highest god. They do not show that the number 60 was thought to confer powers on people or on events.
Mesopotamian scholars also practised divination from the sky and from sheep livers, and they were skilled at astronomical computation. Their number system was a working tool for that. Observations of the planets and the Moon were recorded in sexagesimal notation, and so were calculations of lunar and solar timing.
Mathematics on clay
Two tablets show how far the system could be taken. YBC 7289, an Old Babylonian school tablet in Yale’s collection, shows a square with its diagonals and gives an approximation of the square root of 2 as 1;24,51,10 in sexagesimal. Converted, that is 1 + 24/60 + 51/3,600 + 10/216,000, which is about 1.414213, correct to roughly six decimal places. Plimpton 322, another Old Babylonian tablet, lists numbers that scholars interpret in connection with right triangles, although its exact purpose is still discussed.
What survived
The legacy is easy to see. We divide the hour into 60 minutes and the minute into 60 seconds, and we divide the circle into 360 degrees. Why the circle has 360 degrees is debated. A year of roughly 360 days, ease of division by 60 and Babylonian astronomical practice are all proposed, and no single answer is firmly established. In China, a different 60-part scheme, the sexagenary cycle, developed independently as a way of naming days and years, and it should not be confused with the Mesopotamian system. Across civilizations, numeral systems took many different paths, and base 60 is only one of them.
Six and sixty, then, matter in Mesopotamia because of what they let scribes do. Any claim that six had a special spiritual meaning there goes beyond the surviving evidence.