The CAS Registry Mumber 78134-09-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,8,1,3 and 4 respectively; the second part has 2 digits, 0 and 9 respectively. Calculate Digit Verification of CAS Registry Number 78134-09: (7*7)+(6*8)+(5*1)+(4*3)+(3*4)+(2*0)+(1*9)=135 135 % 10 = 5 So 78134-09-5 is a valid CAS Registry Number.