The CAS Registry Mumber 85717-28-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,5,7,1 and 7 respectively; the second part has 2 digits, 2 and 8 respectively. Calculate Digit Verification of CAS Registry Number 85717-28: (7*8)+(6*5)+(5*7)+(4*1)+(3*7)+(2*2)+(1*8)=158 158 % 10 = 8 So 85717-28-8 is a valid CAS Registry Number.