The CAS Registry Mumber 4364-55-0 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 4,3,6 and 4 respectively; the second part has 2 digits, 5 and 5 respectively. Calculate Digit Verification of CAS Registry Number 4364-55: (6*4)+(5*3)+(4*6)+(3*4)+(2*5)+(1*5)=90 90 % 10 = 0 So 4364-55-0 is a valid CAS Registry Number.