The CAS Registry Mumber 81102-53-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,1,0 and 2 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 81102-53: (7*8)+(6*1)+(5*1)+(4*0)+(3*2)+(2*5)+(1*3)=86 86 % 10 = 6 So 81102-53-6 is a valid CAS Registry Number.