When counting up, it would be difficult to continue indefinitely by giving each new number a new name. This is why numeral systems select one unit as their base number. This idea is the basis of all numeral systems. 

The first tools used in calculations were probably the fingers of the human hand. For this reason, the numeral system we currently use is based on the number ten, which is conveniently the number of human fingers. Other numeral systems have been and continue to be in use, although the decimal system is considered superior to other numeral systems in various ways. In the decimal system, calculations are simple and decimal numbers can be treated in the same way as other numbers. In other numeral systems, the most common base numbers are multiples of five. The connection to the fingers and toes is clear. For example, the number twenty can be indicated as “the number of fingers and toes”.

Several cultures in Australia and Africa still use a pure dual system in which numbers are calculated using only the words denoting the numbers 1 and 2. Words denoting numbers greater than two are formed by forming combinations of the two base numbers. For example, the number five is presented in the form “two-two-one”. The dual system is very impractical for expressing large numbers.

The binary system used in computers is also a dual system, but it differs substantially from the above. The binary system is based on a placeholder and is similar to our decimal system, where the position of a digit in a number indicates what unit of number the digit means. The base number of the binary system is 2. There is no evidence that a binary calculation method has been used in any language.

One interesting numeral system is the 60s, or the sexagesimal system, developed by the Sumerians of Mesopotamia around 3000 BC. Various theories have been put forward as to why the number 60 was so important to the Sumerians. According to one explanation, it was chosen to facilitate divisions because 60 is divisible by a very large number of numbers. While the number 60 seems a strange choice for a base number, the sexagesimal system can still be seen in our measurement system, for example in angular units, minutes, and hours.