The CAS Registry Mumber 81027-65-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,1,0,2 and 7 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 81027-65: (7*8)+(6*1)+(5*0)+(4*2)+(3*7)+(2*6)+(1*5)=108 108 % 10 = 8 So 81027-65-8 is a valid CAS Registry Number.