The CAS Registry Mumber 218444-53-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,1,8,4,4 and 4 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 218444-53: (8*2)+(7*1)+(6*8)+(5*4)+(4*4)+(3*4)+(2*5)+(1*3)=132 132 % 10 = 2 So 218444-53-2 is a valid CAS Registry Number.