The CAS Registry Mumber 54640-82-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,4,6,4 and 0 respectively; the second part has 2 digits, 8 and 2 respectively. Calculate Digit Verification of CAS Registry Number 54640-82: (7*5)+(6*4)+(5*6)+(4*4)+(3*0)+(2*8)+(1*2)=123 123 % 10 = 3 So 54640-82-3 is a valid CAS Registry Number.