The CAS Registry Mumber 191729-86-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,9,1,7,2 and 9 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 191729-86: (8*1)+(7*9)+(6*1)+(5*7)+(4*2)+(3*9)+(2*8)+(1*6)=169 169 % 10 = 9 So 191729-86-9 is a valid CAS Registry Number.