The CAS Registry Mumber 80384-21-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,3,8 and 4 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 80384-21: (7*8)+(6*0)+(5*3)+(4*8)+(3*4)+(2*2)+(1*1)=120 120 % 10 = 0 So 80384-21-0 is a valid CAS Registry Number.