The CAS Registry Mumber 36811-66-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,6,8,1 and 1 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 36811-66: (7*3)+(6*6)+(5*8)+(4*1)+(3*1)+(2*6)+(1*6)=122 122 % 10 = 2 So 36811-66-2 is a valid CAS Registry Number.