The CAS Registry Mumber 881-13-0 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 8,8 and 1 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 881-13: (5*8)+(4*8)+(3*1)+(2*1)+(1*3)=80 80 % 10 = 0 So 881-13-0 is a valid CAS Registry Number.