The CAS Registry Mumber 81176-71-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,1,7 and 6 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 81176-71: (7*8)+(6*1)+(5*1)+(4*7)+(3*6)+(2*7)+(1*1)=128 128 % 10 = 8 So 81176-71-8 is a valid CAS Registry Number.