The CAS Registry Mumber 79677-77-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,9,6,7 and 7 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 79677-77: (7*7)+(6*9)+(5*6)+(4*7)+(3*7)+(2*7)+(1*7)=203 203 % 10 = 3 So 79677-77-3 is a valid CAS Registry Number.