The CAS Registry Mumber 648-24-8 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 6,4 and 8 respectively; the second part has 2 digits, 2 and 4 respectively. Calculate Digit Verification of CAS Registry Number 648-24: (5*6)+(4*4)+(3*8)+(2*2)+(1*4)=78 78 % 10 = 8 So 648-24-8 is a valid CAS Registry Number.