The CAS Registry Mumber 109875-67-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,9,8,7 and 5 respectively; the second part has 2 digits, 6 and 7 respectively. Calculate Digit Verification of CAS Registry Number 109875-67: (8*1)+(7*0)+(6*9)+(5*8)+(4*7)+(3*5)+(2*6)+(1*7)=164 164 % 10 = 4 So 109875-67-4 is a valid CAS Registry Number.