The CAS Registry Mumber 105618-28-8 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,5,6,1 and 8 respectively; the second part has 2 digits, 2 and 8 respectively. Calculate Digit Verification of CAS Registry Number 105618-28: (8*1)+(7*0)+(6*5)+(5*6)+(4*1)+(3*8)+(2*2)+(1*8)=108 108 % 10 = 8 So 105618-28-8 is a valid CAS Registry Number.