The CAS Registry Mumber 83505-35-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,3,5,0 and 5 respectively; the second part has 2 digits, 3 and 5 respectively. Calculate Digit Verification of CAS Registry Number 83505-35: (7*8)+(6*3)+(5*5)+(4*0)+(3*5)+(2*3)+(1*5)=125 125 % 10 = 5 So 83505-35-5 is a valid CAS Registry Number.