The CAS Registry Mumber 109210-45-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,0,9,2,1 and 0 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 109210-45: (8*1)+(7*0)+(6*9)+(5*2)+(4*1)+(3*0)+(2*4)+(1*5)=89 89 % 10 = 9 So 109210-45-9 is a valid CAS Registry Number.