The CAS Registry Mumber 139588-71-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,9,5,8 and 8 respectively; the second part has 2 digits, 7 and 1 respectively. Calculate Digit Verification of CAS Registry Number 139588-71: (8*1)+(7*3)+(6*9)+(5*5)+(4*8)+(3*8)+(2*7)+(1*1)=179 179 % 10 = 9 So 139588-71-9 is a valid CAS Registry Number.