The CAS Registry Mumber 18453-26-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,8,4,5 and 3 respectively; the second part has 2 digits, 2 and 6 respectively. Calculate Digit Verification of CAS Registry Number 18453-26: (7*1)+(6*8)+(5*4)+(4*5)+(3*3)+(2*2)+(1*6)=114 114 % 10 = 4 So 18453-26-4 is a valid CAS Registry Number.