The CAS Registry Mumber 80791-34-0 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 8,0,7,9 and 1 respectively; the second part has 2 digits, 3 and 4 respectively. Calculate Digit Verification of CAS Registry Number 80791-34: (7*8)+(6*0)+(5*7)+(4*9)+(3*1)+(2*3)+(1*4)=140 140 % 10 = 0 So 80791-34-0 is a valid CAS Registry Number.