The CAS Registry Mumber 558459-57-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 5,5,8,4,5 and 9 respectively; the second part has 2 digits, 5 and 7 respectively. Calculate Digit Verification of CAS Registry Number 558459-57: (8*5)+(7*5)+(6*8)+(5*4)+(4*5)+(3*9)+(2*5)+(1*7)=207 207 % 10 = 7 So 558459-57-7 is a valid CAS Registry Number.