<Tr> <Th> Octal </Th> <Td> 22 </Td> </Tr> <Tr> <Th> Duodecimal </Th> <Td> 16 </Td> </Tr> <Tr> <Th> Hexadecimal </Th> <Td> 12 </Td> </Tr> <Tr> <Th> Vigesimal </Th> <Td> </Td> </Tr>

What is the meaning of the number 18