The CAS Registry Mumber 2040-08-6 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,0,4 and 0 respectively; the second part has 2 digits, 0 and 8 respectively. Calculate Digit Verification of CAS Registry Number 2040-08: (6*2)+(5*0)+(4*4)+(3*0)+(2*0)+(1*8)=36 36 % 10 = 6 So 2040-08-6 is a valid CAS Registry Number.