The CAS Registry Mumber 81053-86-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,0,5 and 3 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 81053-86: (7*8)+(6*1)+(5*0)+(4*5)+(3*3)+(2*8)+(1*6)=113 113 % 10 = 3 So 81053-86-3 is a valid CAS Registry Number.