The CAS Registry Mumber 35811-69-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,5,8,1 and 1 respectively; the second part has 2 digits, 6 and 9 respectively. Calculate Digit Verification of CAS Registry Number 35811-69: (7*3)+(6*5)+(5*8)+(4*1)+(3*1)+(2*6)+(1*9)=119 119 % 10 = 9 So 35811-69-9 is a valid CAS Registry Number.