The CAS Registry Mumber 5043-04-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,0,4 and 3 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 5043-04: (6*5)+(5*0)+(4*4)+(3*3)+(2*0)+(1*4)=59 59 % 10 = 9 So 5043-04-9 is a valid CAS Registry Number.