The CAS Registry Mumber 103368-91-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,3,3,6 and 8 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 103368-91: (8*1)+(7*0)+(6*3)+(5*3)+(4*6)+(3*8)+(2*9)+(1*1)=108 108 % 10 = 8 So 103368-91-8 is a valid CAS Registry Number.