The CAS Registry Mumber 77823-76-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,8,2 and 3 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 77823-76: (7*7)+(6*7)+(5*8)+(4*2)+(3*3)+(2*7)+(1*6)=168 168 % 10 = 8 So 77823-76-8 is a valid CAS Registry Number.