The CAS Registry Mumber 7733-30-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,7,3 and 3 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 7733-30: (6*7)+(5*7)+(4*3)+(3*3)+(2*3)+(1*0)=104 104 % 10 = 4 So 7733-30-4 is a valid CAS Registry Number.