The CAS Registry Mumber 82803-90-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,2,8,0 and 3 respectively; the second part has 2 digits, 9 and 0 respectively. Calculate Digit Verification of CAS Registry Number 82803-90: (7*8)+(6*2)+(5*8)+(4*0)+(3*3)+(2*9)+(1*0)=135 135 % 10 = 5 So 82803-90-5 is a valid CAS Registry Number.