The CAS Registry Mumber 3245-91-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 3,2,4 and 5 respectively; the second part has 2 digits, 9 and 1 respectively. Calculate Digit Verification of CAS Registry Number 3245-91: (6*3)+(5*2)+(4*4)+(3*5)+(2*9)+(1*1)=78 78 % 10 = 8 So 3245-91-8 is a valid CAS Registry Number.