The CAS Registry Mumber 123218-01-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,3,2,1 and 8 respectively; the second part has 2 digits, 0 and 1 respectively. Calculate Digit Verification of CAS Registry Number 123218-01: (8*1)+(7*2)+(6*3)+(5*2)+(4*1)+(3*8)+(2*0)+(1*1)=79 79 % 10 = 9 So 123218-01-9 is a valid CAS Registry Number.