The CAS Registry Mumber 64381-57-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 6,4,3,8 and 1 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 64381-57: (7*6)+(6*4)+(5*3)+(4*8)+(3*1)+(2*5)+(1*7)=133 133 % 10 = 3 So 64381-57-3 is a valid CAS Registry Number.