The CAS Registry Mumber 139758-45-5 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,3,9,7,5 and 8 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 139758-45: (8*1)+(7*3)+(6*9)+(5*7)+(4*5)+(3*8)+(2*4)+(1*5)=175 175 % 10 = 5 So 139758-45-5 is a valid CAS Registry Number.