The CAS Registry Mumber 4864-16-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,8,6 and 4 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 4864-16: (6*4)+(5*8)+(4*6)+(3*4)+(2*1)+(1*6)=108 108 % 10 = 8 So 4864-16-8 is a valid CAS Registry Number.