The CAS Registry Mumber 1933-75-1 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,9,3 and 3 respectively; the second part has 2 digits, 7 and 5 respectively. Calculate Digit Verification of CAS Registry Number 1933-75: (6*1)+(5*9)+(4*3)+(3*3)+(2*7)+(1*5)=91 91 % 10 = 1 So 1933-75-1 is a valid CAS Registry Number.