The CAS Registry Mumber 84505-16-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,5,0 and 5 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 84505-16: (7*8)+(6*4)+(5*5)+(4*0)+(3*5)+(2*1)+(1*6)=128 128 % 10 = 8 So 84505-16-8 is a valid CAS Registry Number.