The CAS Registry Mumber 93440-91-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,3,4,4 and 0 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 93440-91: (7*9)+(6*3)+(5*4)+(4*4)+(3*0)+(2*9)+(1*1)=136 136 % 10 = 6 So 93440-91-6 is a valid CAS Registry Number.