The CAS Registry Mumber 223518-41-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,2,3,5,1 and 8 respectively; the second part has 2 digits, 4 and 1 respectively. Calculate Digit Verification of CAS Registry Number 223518-41: (8*2)+(7*2)+(6*3)+(5*5)+(4*1)+(3*8)+(2*4)+(1*1)=110 110 % 10 = 0 So 223518-41-0 is a valid CAS Registry Number.