The CAS Registry Mumber 73791-74-9 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,7,9 and 1 respectively; the second part has 2 digits, 7 and 4 respectively. Calculate Digit Verification of CAS Registry Number 73791-74: (7*7)+(6*3)+(5*7)+(4*9)+(3*1)+(2*7)+(1*4)=159 159 % 10 = 9 So 73791-74-9 is a valid CAS Registry Number.