The CAS Registry Mumber 83511-23-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,3,5,1 and 1 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 83511-23: (7*8)+(6*3)+(5*5)+(4*1)+(3*1)+(2*2)+(1*3)=113 113 % 10 = 3 So 83511-23-3 is a valid CAS Registry Number.