The CAS Registry Mumber 4445-33-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,4,4 and 5 respectively; the second part has 2 digits, 3 and 3 respectively. Calculate Digit Verification of CAS Registry Number 4445-33: (6*4)+(5*4)+(4*4)+(3*5)+(2*3)+(1*3)=84 84 % 10 = 4 So 4445-33-4 is a valid CAS Registry Number.