The CAS Registry Mumber 123354-97-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,3,3,5 and 4 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 123354-97: (8*1)+(7*2)+(6*3)+(5*3)+(4*5)+(3*4)+(2*9)+(1*7)=112 112 % 10 = 2 So 123354-97-2 is a valid CAS Registry Number.