The CAS Registry Mumber 73843-66-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,8,4 and 3 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 73843-66: (7*7)+(6*3)+(5*8)+(4*4)+(3*3)+(2*6)+(1*6)=150 150 % 10 = 0 So 73843-66-0 is a valid CAS Registry Number.