The CAS Registry Mumber 2240-02-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,2,4 and 0 respectively; the second part has 2 digits, 0 and 2 respectively. Calculate Digit Verification of CAS Registry Number 2240-02: (6*2)+(5*2)+(4*4)+(3*0)+(2*0)+(1*2)=40 40 % 10 = 0 So 2240-02-0 is a valid CAS Registry Number.