The CAS Registry Mumber 43218-72-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,3,2,1 and 8 respectively; the second part has 2 digits, 7 and 2 respectively. Calculate Digit Verification of CAS Registry Number 43218-72: (7*4)+(6*3)+(5*2)+(4*1)+(3*8)+(2*7)+(1*2)=100 100 % 10 = 0 So 43218-72-0 is a valid CAS Registry Number.