The CAS Registry Mumber 104417-78-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,4,4,1 and 7 respectively; the second part has 2 digits, 7 and 8 respectively. Calculate Digit Verification of CAS Registry Number 104417-78: (8*1)+(7*0)+(6*4)+(5*4)+(4*1)+(3*7)+(2*7)+(1*8)=99 99 % 10 = 9 So 104417-78-9 is a valid CAS Registry Number.