The CAS Registry Mumber 135080-43-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,5,0,8 and 0 respectively; the second part has 2 digits, 4 and 3 respectively. Calculate Digit Verification of CAS Registry Number 135080-43: (8*1)+(7*3)+(6*5)+(5*0)+(4*8)+(3*0)+(2*4)+(1*3)=102 102 % 10 = 2 So 135080-43-2 is a valid CAS Registry Number.