The CAS Registry Mumber 97351-71-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,7,3,5 and 1 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 97351-71: (7*9)+(6*7)+(5*3)+(4*5)+(3*1)+(2*7)+(1*1)=158 158 % 10 = 8 So 97351-71-8 is a valid CAS Registry Number.