CAS registry number

A CAS registry number is a unique number given to every chemical substance by the Chemical Abstracts Service (CAS). It is also called CASRN or CAS number. CAS registry number is also given to organic, inorganic compounds, minerals, isotopes, alloys. They are numbers ending with a check digit. They do not contain any structure information of the chemical.
It now identifies more than 164 million organic and inorganic substances. 68 million protein and DNA sequences are identified also. It is updated with around 15,000 new substances everyday.