The CAS Registry Mumber 104944-21-0 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,4,9,4 and 4 respectively; the second part has 2 digits, 2 and 1 respectively. Calculate Digit Verification of CAS Registry Number 104944-21: (8*1)+(7*0)+(6*4)+(5*9)+(4*4)+(3*4)+(2*2)+(1*1)=110 110 % 10 = 0 So 104944-21-0 is a valid CAS Registry Number.