The CAS Registry Mumber 233662-89-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,3,3,6,6 and 2 respectively; the second part has 2 digits, 8 and 9 respectively. Calculate Digit Verification of CAS Registry Number 233662-89: (8*2)+(7*3)+(6*3)+(5*6)+(4*6)+(3*2)+(2*8)+(1*9)=140 140 % 10 = 0 So 233662-89-0 is a valid CAS Registry Number.