The CAS Registry Mumber 5531-38-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,5,3 and 1 respectively; the second part has 2 digits, 3 and 8 respectively. Calculate Digit Verification of CAS Registry Number 5531-38: (6*5)+(5*5)+(4*3)+(3*1)+(2*3)+(1*8)=84 84 % 10 = 4 So 5531-38-4 is a valid CAS Registry Number.