The CAS Registry Mumber 129256-80-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,9,2,5 and 6 respectively; the second part has 2 digits, 8 and 0 respectively. Calculate Digit Verification of CAS Registry Number 129256-80: (8*1)+(7*2)+(6*9)+(5*2)+(4*5)+(3*6)+(2*8)+(1*0)=140 140 % 10 = 0 So 129256-80-0 is a valid CAS Registry Number.