The CAS Registry Mumber 75517-77-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,5,1 and 7 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 75517-77: (7*7)+(6*5)+(5*5)+(4*1)+(3*7)+(2*7)+(1*7)=150 150 % 10 = 0 So 75517-77-0 is a valid CAS Registry Number.