The CAS Registry Mumber 134789-97-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,4,7,8 and 9 respectively; the second part has 2 digits, 9 and 7 respectively. Calculate Digit Verification of CAS Registry Number 134789-97: (8*1)+(7*3)+(6*4)+(5*7)+(4*8)+(3*9)+(2*9)+(1*7)=172 172 % 10 = 2 So 134789-97-2 is a valid CAS Registry Number.