The CAS Registry Mumber 184221-88-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,4,2,2 and 1 respectively; the second part has 2 digits, 8 and 8 respectively. Calculate Digit Verification of CAS Registry Number 184221-88: (8*1)+(7*8)+(6*4)+(5*2)+(4*2)+(3*1)+(2*8)+(1*8)=133 133 % 10 = 3 So 184221-88-3 is a valid CAS Registry Number.