The CAS Registry Mumber 67133-56-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,7,1,3 and 3 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 67133-56: (7*6)+(6*7)+(5*1)+(4*3)+(3*3)+(2*5)+(1*6)=126 126 % 10 = 6 So 67133-56-6 is a valid CAS Registry Number.