The CAS Registry Mumber 4803-23-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,8,0 and 3 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 4803-23: (6*4)+(5*8)+(4*0)+(3*3)+(2*2)+(1*3)=80 80 % 10 = 0 So 4803-23-0 is a valid CAS Registry Number.