The CAS Registry Mumber 98186-17-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,8,1,8 and 6 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 98186-17: (7*9)+(6*8)+(5*1)+(4*8)+(3*6)+(2*1)+(1*7)=175 175 % 10 = 5 So 98186-17-5 is a valid CAS Registry Number.