The CAS Registry Mumber 40017-81-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,0,0,1 and 7 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 40017-81: (7*4)+(6*0)+(5*0)+(4*1)+(3*7)+(2*8)+(1*1)=70 70 % 10 = 0 So 40017-81-0 is a valid CAS Registry Number.