The CAS Registry Mumber 66723-82-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,6,7,2 and 3 respectively; the second part has 2 digits, 8 and 2 respectively. Calculate Digit Verification of CAS Registry Number 66723-82: (7*6)+(6*6)+(5*7)+(4*2)+(3*3)+(2*8)+(1*2)=148 148 % 10 = 8 So 66723-82-8 is a valid CAS Registry Number.