The CAS Registry Mumber 68916-81-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,9,1 and 6 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 68916-81: (7*6)+(6*8)+(5*9)+(4*1)+(3*6)+(2*8)+(1*1)=174 174 % 10 = 4 So 68916-81-4 is a valid CAS Registry Number.