The CAS Registry Mumber 10599-81-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,0,5,9 and 9 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 10599-81: (7*1)+(6*0)+(5*5)+(4*9)+(3*9)+(2*8)+(1*1)=112 112 % 10 = 2 So 10599-81-2 is a valid CAS Registry Number.