The CAS Registry Mumber 86823-86-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,6,8,2 and 3 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 86823-86: (7*8)+(6*6)+(5*8)+(4*2)+(3*3)+(2*8)+(1*6)=171 171 % 10 = 1 So 86823-86-1 is a valid CAS Registry Number.