The CAS Registry Mumber 71687-02-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,1,6,8 and 7 respectively; the second part has 2 digits, 0 and 2 respectively. Calculate Digit Verification of CAS Registry Number 71687-02: (7*7)+(6*1)+(5*6)+(4*8)+(3*7)+(2*0)+(1*2)=140 140 % 10 = 0 So 71687-02-0 is a valid CAS Registry Number.