The CAS Registry Mumber 86891-16-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,6,8,9 and 1 respectively; the second part has 2 digits, 1 and 6 respectively. Calculate Digit Verification of CAS Registry Number 86891-16: (7*8)+(6*6)+(5*8)+(4*9)+(3*1)+(2*1)+(1*6)=179 179 % 10 = 9 So 86891-16-9 is a valid CAS Registry Number.