The CAS Registry Mumber 129885-91-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,9,8,8 and 5 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 129885-91: (8*1)+(7*2)+(6*9)+(5*8)+(4*8)+(3*5)+(2*9)+(1*1)=182 182 % 10 = 2 So 129885-91-2 is a valid CAS Registry Number.