The CAS Registry Mumber 73277-77-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,2,7 and 7 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 73277-77: (7*7)+(6*3)+(5*2)+(4*7)+(3*7)+(2*7)+(1*7)=147 147 % 10 = 7 So 73277-77-7 is a valid CAS Registry Number.