The CAS Registry Mumber 52164-53-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,2,1,6 and 4 respectively; the second part has 2 digits, 5 and 3 respectively. Calculate Digit Verification of CAS Registry Number 52164-53: (7*5)+(6*2)+(5*1)+(4*6)+(3*4)+(2*5)+(1*3)=101 101 % 10 = 1 So 52164-53-1 is a valid CAS Registry Number.