The CAS Registry Mumber 112561-84-9 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,2,5,6 and 1 respectively; the second part has 2 digits, 8 and 4 respectively. Calculate Digit Verification of CAS Registry Number 112561-84: (8*1)+(7*1)+(6*2)+(5*5)+(4*6)+(3*1)+(2*8)+(1*4)=99 99 % 10 = 9 So 112561-84-9 is a valid CAS Registry Number.