The CAS Registry Mumber 68168-19-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,8,1,6 and 8 respectively; the second part has 2 digits, 1 and 9 respectively. Calculate Digit Verification of CAS Registry Number 68168-19: (7*6)+(6*8)+(5*1)+(4*6)+(3*8)+(2*1)+(1*9)=154 154 % 10 = 4 So 68168-19-4 is a valid CAS Registry Number.