The CAS Registry Mumber 81016-54-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,0,1 and 6 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 81016-54: (7*8)+(6*1)+(5*0)+(4*1)+(3*6)+(2*5)+(1*4)=98 98 % 10 = 8 So 81016-54-8 is a valid CAS Registry Number.