The CAS Registry Mumber 4083-65-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,0,8 and 3 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 4083-65: (6*4)+(5*0)+(4*8)+(3*3)+(2*6)+(1*5)=82 82 % 10 = 2 So 4083-65-2 is a valid CAS Registry Number.