The CAS Registry Mumber 182153-75-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,8,2,1,5 and 3 respectively; the second part has 2 digits, 7 and 5 respectively. Calculate Digit Verification of CAS Registry Number 182153-75: (8*1)+(7*8)+(6*2)+(5*1)+(4*5)+(3*3)+(2*7)+(1*5)=129 129 % 10 = 9 So 182153-75-9 is a valid CAS Registry Number.