The CAS Registry Mumber 2544-61-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,5,4 and 4 respectively; the second part has 2 digits, 6 and 1 respectively. Calculate Digit Verification of CAS Registry Number 2544-61: (6*2)+(5*5)+(4*4)+(3*4)+(2*6)+(1*1)=78 78 % 10 = 8 So 2544-61-8 is a valid CAS Registry Number.