The CAS Registry Mumber 69813-31-6 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,9,8,1 and 3 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 69813-31: (7*6)+(6*9)+(5*8)+(4*1)+(3*3)+(2*3)+(1*1)=156 156 % 10 = 6 So 69813-31-6 is a valid CAS Registry Number.