The CAS Registry Mumber 123041-84-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,2,3,0,4 and 1 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 123041-84: (8*1)+(7*2)+(6*3)+(5*0)+(4*4)+(3*1)+(2*8)+(1*4)=79 79 % 10 = 9 So 123041-84-9 is a valid CAS Registry Number.