The CAS Registry Mumber 109687-40-3 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,9,6,8 and 7 respectively; the second part has 2 digits, 4 and 0 respectively. Calculate Digit Verification of CAS Registry Number 109687-40: (8*1)+(7*0)+(6*9)+(5*6)+(4*8)+(3*7)+(2*4)+(1*0)=153 153 % 10 = 3 So 109687-40-3 is a valid CAS Registry Number.