The CAS Registry Mumber 392-66-5 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 3,9 and 2 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 392-66: (5*3)+(4*9)+(3*2)+(2*6)+(1*6)=75 75 % 10 = 5 So 392-66-5 is a valid CAS Registry Number.