The CAS Registry Mumber 186393-17-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,6,3,9 and 3 respectively; the second part has 2 digits, 1 and 7 respectively. Calculate Digit Verification of CAS Registry Number 186393-17: (8*1)+(7*8)+(6*6)+(5*3)+(4*9)+(3*3)+(2*1)+(1*7)=169 169 % 10 = 9 So 186393-17-9 is a valid CAS Registry Number.