The CAS Registry Mumber 4078-66-4 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,0,7 and 8 respectively; the second part has 2 digits, 6 and 6 respectively. Calculate Digit Verification of CAS Registry Number 4078-66: (6*4)+(5*0)+(4*7)+(3*8)+(2*6)+(1*6)=94 94 % 10 = 4 So 4078-66-4 is a valid CAS Registry Number.