The CAS Registry Mumber 104417-81-4 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, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 104417-81: (8*1)+(7*0)+(6*4)+(5*4)+(4*1)+(3*7)+(2*8)+(1*1)=94 94 % 10 = 4 So 104417-81-4 is a valid CAS Registry Number.