The CAS Registry Mumber 59404-31-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,9,4,0 and 4 respectively; the second part has 2 digits, 3 and 1 respectively. Calculate Digit Verification of CAS Registry Number 59404-31: (7*5)+(6*9)+(5*4)+(4*0)+(3*4)+(2*3)+(1*1)=128 128 % 10 = 8 So 59404-31-8 is a valid CAS Registry Number.