The CAS Registry Mumber 884-51-5 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 8,8 and 4 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 884-51: (5*8)+(4*8)+(3*4)+(2*5)+(1*1)=95 95 % 10 = 5 So 884-51-5 is a valid CAS Registry Number.