The CAS Registry Mumber 74105-06-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,1,0 and 5 respectively; the second part has 2 digits, 0 and 6 respectively. Calculate Digit Verification of CAS Registry Number 74105-06: (7*7)+(6*4)+(5*1)+(4*0)+(3*5)+(2*0)+(1*6)=99 99 % 10 = 9 So 74105-06-9 is a valid CAS Registry Number.