The CAS Registry Mumber 81411-31-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,4,1 and 1 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 81411-31: (7*8)+(6*1)+(5*4)+(4*1)+(3*1)+(2*3)+(1*1)=96 96 % 10 = 6 So 81411-31-6 is a valid CAS Registry Number.