The CAS Registry Mumber 168566-19-6 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,6,8,5,6 and 6 respectively; the second part has 2 digits, 1 and 9 respectively. Calculate Digit Verification of CAS Registry Number 168566-19: (8*1)+(7*6)+(6*8)+(5*5)+(4*6)+(3*6)+(2*1)+(1*9)=176 176 % 10 = 6 So 168566-19-6 is a valid CAS Registry Number.