The CAS Registry Mumber 85553-74-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,5,5,5 and 3 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 85553-74: (7*8)+(6*5)+(5*5)+(4*5)+(3*3)+(2*7)+(1*4)=158 158 % 10 = 8 So 85553-74-8 is a valid CAS Registry Number.