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The {\em duodecimal system} is a positional number system with base 12, using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A and B.

The \PMlinkescapetext{term} duodecimal comes fro Latin.\, There is also a less used synonym {\em duodecadic} mixed of a Latin begin and a Greek end and still a purely Greek \PMlinkescapetext{formation} {\em dodecadic}.

Some divisibility tests in duodecimal are:

$n$ is divisible by 2 if its least significant digit is 0, 2, 4, 6, 8 or A.

$n$ is divisible by 3 if its least significant digit is 0, 3, 6 or 9.

$n$ is divisible by 4 if its least significant digit is 0, 4 or 8.

$n$ is divisible by 6 if its least significant digit is 0 or 6.

$n$ is divisible by 11 if it has digital root B.

$n$ is of course divisible by 12 if it ends in a 0.

$n$ is divisible by 13 if the difference of the odd placed digits and the even place digits of $n$ is a multiple of 13.