The CAS Registry Mumber 105905-76-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,5,9,0 and 5 respectively; the second part has 2 digits, 7 and 6 respectively. Calculate Digit Verification of CAS Registry Number 105905-76: (8*1)+(7*0)+(6*5)+(5*9)+(4*0)+(3*5)+(2*7)+(1*6)=118 118 % 10 = 8 So 105905-76-8 is a valid CAS Registry Number.