The CAS Registry Mumber 80008-31-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,0,0 and 8 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 80008-31: (7*8)+(6*0)+(5*0)+(4*0)+(3*8)+(2*3)+(1*1)=87 87 % 10 = 7 So 80008-31-7 is a valid CAS Registry Number.