The CAS Registry Mumber 134789-98-3 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 8 respectively. Calculate Digit Verification of CAS Registry Number 134789-98: (8*1)+(7*3)+(6*4)+(5*7)+(4*8)+(3*9)+(2*9)+(1*8)=173 173 % 10 = 3 So 134789-98-3 is a valid CAS Registry Number.