The CAS Registry Mumber 55724-44-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,7,2 and 4 respectively; the second part has 2 digits, 4 and 4 respectively. Calculate Digit Verification of CAS Registry Number 55724-44: (7*5)+(6*5)+(5*7)+(4*2)+(3*4)+(2*4)+(1*4)=132 132 % 10 = 2 So 55724-44-2 is a valid CAS Registry Number.