The CAS Registry Mumber 65779-65-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,5,7,7 and 9 respectively; the second part has 2 digits, 6 and 5 respectively. Calculate Digit Verification of CAS Registry Number 65779-65: (7*6)+(6*5)+(5*7)+(4*7)+(3*9)+(2*6)+(1*5)=179 179 % 10 = 9 So 65779-65-9 is a valid CAS Registry Number.