The CAS Registry Mumber 35498-66-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,5,4,9 and 8 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 35498-66: (7*3)+(6*5)+(5*4)+(4*9)+(3*8)+(2*6)+(1*6)=149 149 % 10 = 9 So 35498-66-9 is a valid CAS Registry Number.