The CAS Registry Mumber 54026-87-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,4,0,2 and 6 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 54026-87: (7*5)+(6*4)+(5*0)+(4*2)+(3*6)+(2*8)+(1*7)=108 108 % 10 = 8 So 54026-87-8 is a valid CAS Registry Number.