The CAS Registry Mumber 728030-27-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 7,2,8,0,3 and 0 respectively; the second part has 2 digits, 2 and 7 respectively. Calculate Digit Verification of CAS Registry Number 728030-27: (8*7)+(7*2)+(6*8)+(5*0)+(4*3)+(3*0)+(2*2)+(1*7)=141 141 % 10 = 1 So 728030-27-1 is a valid CAS Registry Number.