The CAS Registry Mumber 99422-81-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,4,2 and 2 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 99422-81: (7*9)+(6*9)+(5*4)+(4*2)+(3*2)+(2*8)+(1*1)=168 168 % 10 = 8 So 99422-81-8 is a valid CAS Registry Number.