The CAS Registry Mumber 283163-01-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,8,3,1,6 and 3 respectively; the second part has 2 digits, 0 and 1 respectively. Calculate Digit Verification of CAS Registry Number 283163-01: (8*2)+(7*8)+(6*3)+(5*1)+(4*6)+(3*3)+(2*0)+(1*1)=129 129 % 10 = 9 So 283163-01-9 is a valid CAS Registry Number.