The CAS Registry Mumber 857899-86-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 8,5,7,8,9 and 9 respectively; the second part has 2 digits, 8 and 6 respectively. Calculate Digit Verification of CAS Registry Number 857899-86: (8*8)+(7*5)+(6*7)+(5*8)+(4*9)+(3*9)+(2*8)+(1*6)=266 266 % 10 = 6 So 857899-86-6 is a valid CAS Registry Number.