The CAS Registry Mumber 9008-23-5 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 9,0,0 and 8 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 9008-23: (6*9)+(5*0)+(4*0)+(3*8)+(2*2)+(1*3)=85 85 % 10 = 5 So 9008-23-5 is a valid CAS Registry Number.