The CAS Registry Mumber 113445-87-7 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 1,1,3,4,4 and 5 respectively; the second part has 2 digits, 8 and 7 respectively. Calculate Digit Verification of CAS Registry Number 113445-87: (8*1)+(7*1)+(6*3)+(5*4)+(4*4)+(3*5)+(2*8)+(1*7)=107 107 % 10 = 7 So 113445-87-7 is a valid CAS Registry Number.