The CAS Registry Mumber 40017-78-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 4,0,0,1 and 7 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 40017-78: (7*4)+(6*0)+(5*0)+(4*1)+(3*7)+(2*7)+(1*8)=75 75 % 10 = 5 So 40017-78-5 is a valid CAS Registry Number.