The CAS Registry Mumber 4148-24-7 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,1,4 and 8 respectively; the second part has 2 digits, 2 and 4 respectively. Calculate Digit Verification of CAS Registry Number 4148-24: (6*4)+(5*1)+(4*4)+(3*8)+(2*2)+(1*4)=77 77 % 10 = 7 So 4148-24-7 is a valid CAS Registry Number.