The CAS Registry Mumber 80206-83-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,2,0 and 6 respectively; the second part has 2 digits, 8 and 3 respectively. Calculate Digit Verification of CAS Registry Number 80206-83: (7*8)+(6*0)+(5*2)+(4*0)+(3*6)+(2*8)+(1*3)=103 103 % 10 = 3 So 80206-83-3 is a valid CAS Registry Number.