The CAS Registry Mumber 67665-59-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,7,6,6 and 5 respectively; the second part has 2 digits, 5 and 9 respectively. Calculate Digit Verification of CAS Registry Number 67665-59: (7*6)+(6*7)+(5*6)+(4*6)+(3*5)+(2*5)+(1*9)=172 172 % 10 = 2 So 67665-59-2 is a valid CAS Registry Number.