The CAS Registry Mumber 128346-36-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,8,3,4 and 6 respectively; the second part has 2 digits, 3 and 6 respectively. Calculate Digit Verification of CAS Registry Number 128346-36: (8*1)+(7*2)+(6*8)+(5*3)+(4*4)+(3*6)+(2*3)+(1*6)=131 131 % 10 = 1 So 128346-36-1 is a valid CAS Registry Number.