The CAS Registry Mumber 33256-35-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,3,2,5 and 6 respectively; the second part has 2 digits, 3 and 5 respectively. Calculate Digit Verification of CAS Registry Number 33256-35: (7*3)+(6*3)+(5*2)+(4*5)+(3*6)+(2*3)+(1*5)=98 98 % 10 = 8 So 33256-35-8 is a valid CAS Registry Number.