The CAS Registry Mumber 76776-82-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,7,7 and 6 respectively; the second part has 2 digits, 8 and 2 respectively. Calculate Digit Verification of CAS Registry Number 76776-82: (7*7)+(6*6)+(5*7)+(4*7)+(3*6)+(2*8)+(1*2)=184 184 % 10 = 4 So 76776-82-4 is a valid CAS Registry Number.