The CAS Registry Mumber 134161-68-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,4,1,6 and 1 respectively; the second part has 2 digits, 6 and 8 respectively. Calculate Digit Verification of CAS Registry Number 134161-68: (8*1)+(7*3)+(6*4)+(5*1)+(4*6)+(3*1)+(2*6)+(1*8)=105 105 % 10 = 5 So 134161-68-5 is a valid CAS Registry Number.