The CAS Registry Mumber 111299-31-1 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,1,2,9 and 9 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 111299-31: (8*1)+(7*1)+(6*1)+(5*2)+(4*9)+(3*9)+(2*3)+(1*1)=101 101 % 10 = 1 So 111299-31-1 is a valid CAS Registry Number.