The CAS Registry Mumber 81053-78-3 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, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 81053-78: (7*8)+(6*1)+(5*0)+(4*5)+(3*3)+(2*7)+(1*8)=113 113 % 10 = 3 So 81053-78-3 is a valid CAS Registry Number.