The CAS Registry Mumber 945-40-4 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 9,4 and 5 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 945-40: (5*9)+(4*4)+(3*5)+(2*4)+(1*0)=84 84 % 10 = 4 So 945-40-4 is a valid CAS Registry Number.