The CAS Registry Mumber 53771-02-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,3,7,7 and 1 respectively; the second part has 2 digits, 0 and 2 respectively. Calculate Digit Verification of CAS Registry Number 53771-02: (7*5)+(6*3)+(5*7)+(4*7)+(3*1)+(2*0)+(1*2)=121 121 % 10 = 1 So 53771-02-1 is a valid CAS Registry Number.