The CAS Registry Mumber 77252-99-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,7,2,5 and 2 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 77252-99: (7*7)+(6*7)+(5*2)+(4*5)+(3*2)+(2*9)+(1*9)=154 154 % 10 = 4 So 77252-99-4 is a valid CAS Registry Number.