The CAS Registry Mumber 84200-51-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,4,2,0 and 0 respectively; the second part has 2 digits, 5 and 1 respectively. Calculate Digit Verification of CAS Registry Number 84200-51: (7*8)+(6*4)+(5*2)+(4*0)+(3*0)+(2*5)+(1*1)=101 101 % 10 = 1 So 84200-51-1 is a valid CAS Registry Number.