The CAS Registry Mumber 55572-13-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,5,7 and 2 respectively; the second part has 2 digits, 1 and 3 respectively. Calculate Digit Verification of CAS Registry Number 55572-13: (7*5)+(6*5)+(5*5)+(4*7)+(3*2)+(2*1)+(1*3)=129 129 % 10 = 9 So 55572-13-9 is a valid CAS Registry Number.