The CAS Registry Mumber 87908-33-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,7,9,0 and 8 respectively; the second part has 2 digits, 3 and 3 respectively. Calculate Digit Verification of CAS Registry Number 87908-33: (7*8)+(6*7)+(5*9)+(4*0)+(3*8)+(2*3)+(1*3)=176 176 % 10 = 6 So 87908-33-6 is a valid CAS Registry Number.