num2str(12​3456789012​3456789) returns '1234567890123456768'

Please help: command num2str(1234567890123456789) on matlab returns '1234567890123456768'...seems to be some overflow error, as last two digits have got changes from 89 to 68.

Answer 1

[Jan]

Exactly. Matlab stores the values in the IEEE754 format, which use about 16 digits. This is the standard format for floating point numbers, such that this is not a problem of Matlab but a general decision for numerical software.

See https://www.mathworks.com/help/symbolic/vpa.html for using number with more digits.