The CAS Registry Mumber 18033-98-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,0,3 and 3 respectively; the second part has 2 digits, 9 and 8 respectively. Calculate Digit Verification of CAS Registry Number 18033-98: (7*1)+(6*8)+(5*0)+(4*3)+(3*3)+(2*9)+(1*8)=102 102 % 10 = 2 So 18033-98-2 is a valid CAS Registry Number.