The CAS Registry Mumber 40299-20-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,0,2,9 and 9 respectively; the second part has 2 digits, 2 and 0 respectively. Calculate Digit Verification of CAS Registry Number 40299-20: (7*4)+(6*0)+(5*2)+(4*9)+(3*9)+(2*2)+(1*0)=105 105 % 10 = 5 So 40299-20-5 is a valid CAS Registry Number.