The CAS Registry Mumber 113444-34-1 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 4 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 113444-34: (8*1)+(7*1)+(6*3)+(5*4)+(4*4)+(3*4)+(2*3)+(1*4)=91 91 % 10 = 1 So 113444-34-1 is a valid CAS Registry Number.