The CAS Registry Mumber 116161-54-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,6,1,6 and 1 respectively; the second part has 2 digits, 5 and 4 respectively. Calculate Digit Verification of CAS Registry Number 116161-54: (8*1)+(7*1)+(6*6)+(5*1)+(4*6)+(3*1)+(2*5)+(1*4)=97 97 % 10 = 7 So 116161-54-7 is a valid CAS Registry Number.