The CAS Registry Mumber 99507-57-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,5,0 and 7 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 99507-57: (7*9)+(6*9)+(5*5)+(4*0)+(3*7)+(2*5)+(1*7)=180 180 % 10 = 0 So 99507-57-0 is a valid CAS Registry Number.