The CAS Registry Mumber 106087-99-4 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,6,0,8 and 7 respectively; the second part has 2 digits, 9 and 9 respectively. Calculate Digit Verification of CAS Registry Number 106087-99: (8*1)+(7*0)+(6*6)+(5*0)+(4*8)+(3*7)+(2*9)+(1*9)=124 124 % 10 = 4 So 106087-99-4 is a valid CAS Registry Number.