The CAS Registry Mumber 38931-64-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 3,8,9,3 and 1 respectively; the second part has 2 digits, 6 and 4 respectively. Calculate Digit Verification of CAS Registry Number 38931-64: (7*3)+(6*8)+(5*9)+(4*3)+(3*1)+(2*6)+(1*4)=145 145 % 10 = 5 So 38931-64-5 is a valid CAS Registry Number.