The CAS Registry Mumber 51805-02-8 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 5,1,8,0 and 5 respectively; the second part has 2 digits, 0 and 2 respectively. Calculate Digit Verification of CAS Registry Number 51805-02: (7*5)+(6*1)+(5*8)+(4*0)+(3*5)+(2*0)+(1*2)=98 98 % 10 = 8 So 51805-02-8 is a valid CAS Registry Number.