The CAS Registry Mumber 537-93-9 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 5,3 and 7 respectively; the second part has 2 digits, 9 and 3 respectively. Calculate Digit Verification of CAS Registry Number 537-93: (5*5)+(4*3)+(3*7)+(2*9)+(1*3)=79 79 % 10 = 9 So 537-93-9 is a valid CAS Registry Number.