The CAS Registry Mumber 13421-96-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,3,4,2 and 1 respectively; the second part has 2 digits, 9 and 6 respectively. Calculate Digit Verification of CAS Registry Number 13421-96: (7*1)+(6*3)+(5*4)+(4*2)+(3*1)+(2*9)+(1*6)=80 80 % 10 = 0 So 13421-96-0 is a valid CAS Registry Number.