The CAS Registry Mumber 5122-18-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 5,1,2 and 2 respectively; the second part has 2 digits, 1 and 8 respectively. Calculate Digit Verification of CAS Registry Number 5122-18: (6*5)+(5*1)+(4*2)+(3*2)+(2*1)+(1*8)=59 59 % 10 = 9 So 5122-18-9 is a valid CAS Registry Number.