The CAS Registry Mumber 54658-08-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,4,6,5 and 8 respectively; the second part has 2 digits, 0 and 8 respectively. Calculate Digit Verification of CAS Registry Number 54658-08: (7*5)+(6*4)+(5*6)+(4*5)+(3*8)+(2*0)+(1*8)=141 141 % 10 = 1 So 54658-08-1 is a valid CAS Registry Number.