The CAS Registry Mumber 93898-15-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,3,8,9 and 8 respectively; the second part has 2 digits, 1 and 5 respectively. Calculate Digit Verification of CAS Registry Number 93898-15: (7*9)+(6*3)+(5*8)+(4*9)+(3*8)+(2*1)+(1*5)=188 188 % 10 = 8 So 93898-15-8 is a valid CAS Registry Number.