The CAS Registry Mumber 72496-81-2 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,2,4,9 and 6 respectively; the second part has 2 digits, 8 and 1 respectively. Calculate Digit Verification of CAS Registry Number 72496-81: (7*7)+(6*2)+(5*4)+(4*9)+(3*6)+(2*8)+(1*1)=152 152 % 10 = 2 So 72496-81-2 is a valid CAS Registry Number.