The CAS Registry Mumber 89810-76-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,9,8,1 and 0 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 89810-76: (7*8)+(6*9)+(5*8)+(4*1)+(3*0)+(2*7)+(1*6)=174 174 % 10 = 4 So 89810-76-4 is a valid CAS Registry Number.