The CAS Registry Mumber 9000-35-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 9,0,0 and 0 respectively; the second part has 2 digits, 3 and 5 respectively. Calculate Digit Verification of CAS Registry Number 9000-35: (6*9)+(5*0)+(4*0)+(3*0)+(2*3)+(1*5)=65 65 % 10 = 5 So 9000-35-5 is a valid CAS Registry Number.