The CAS Registry Mumber 99054-52-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 9,9,0,5 and 4 respectively; the second part has 2 digits, 5 and 2 respectively. Calculate Digit Verification of CAS Registry Number 99054-52: (7*9)+(6*9)+(5*0)+(4*5)+(3*4)+(2*5)+(1*2)=161 161 % 10 = 1 So 99054-52-1 is a valid CAS Registry Number.