The CAS Registry Mumber 204381-32-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 2,0,4,3,8 and 1 respectively; the second part has 2 digits, 3 and 2 respectively. Calculate Digit Verification of CAS Registry Number 204381-32: (8*2)+(7*0)+(6*4)+(5*3)+(4*8)+(3*1)+(2*3)+(1*2)=98 98 % 10 = 8 So 204381-32-8 is a valid CAS Registry Number.