CAS registry number

A CAS registry number is a unique number given to every chemical substance by the Chemical Abstracts Service (CAS).^[1] 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.^[2]

It now identifies more than 164 million organic and inorganic substances. 68 million protein and DNA sequences are identified also.^[2] It is updated with around 15,000 new substances everyday.^[1]