The CAS Registry Mumber 128470-61-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,4,7 and 0 respectively; the second part has 2 digits, 6 and 1 respectively. Calculate Digit Verification of CAS Registry Number 128470-61: (8*1)+(7*2)+(6*8)+(5*4)+(4*7)+(3*0)+(2*6)+(1*1)=131 131 % 10 = 1 So 128470-61-1 is a valid CAS Registry Number.