The CAS Registry Mumber 129665-97-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,9,6,6 and 5 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 129665-97: (8*1)+(7*2)+(6*9)+(5*6)+(4*6)+(3*5)+(2*9)+(1*7)=170 170 % 10 = 0 So 129665-97-0 is a valid CAS Registry Number.