The CAS Registry Mumber 55898-45-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,5,8,9 and 8 respectively; the second part has 2 digits, 4 and 5 respectively. Calculate Digit Verification of CAS Registry Number 55898-45: (7*5)+(6*5)+(5*8)+(4*9)+(3*8)+(2*4)+(1*5)=178 178 % 10 = 8 So 55898-45-8 is a valid CAS Registry Number.