The CAS Registry Mumber 128175-79-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,1,7 and 5 respectively; the second part has 2 digits, 7 and 9 respectively. Calculate Digit Verification of CAS Registry Number 128175-79: (8*1)+(7*2)+(6*8)+(5*1)+(4*7)+(3*5)+(2*7)+(1*9)=141 141 % 10 = 1 So 128175-79-1 is a valid CAS Registry Number.