The CAS Registry Mumber 76766-04-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,6,7,6 and 6 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 76766-04: (7*7)+(6*6)+(5*7)+(4*6)+(3*6)+(2*0)+(1*4)=166 166 % 10 = 6 So 76766-04-6 is a valid CAS Registry Number.