The CAS Registry Mumber 2504-53-2 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,5,0 and 4 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 2504-53: (6*2)+(5*5)+(4*0)+(3*4)+(2*5)+(1*3)=62 62 % 10 = 2 So 2504-53-2 is a valid CAS Registry Number.