The CAS Registry Mumber 797798-56-2 includes 9 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 6 digits, 7,9,7,7,9 and 8 respectively; the second part has 2 digits, 5 and 6 respectively. Calculate Digit Verification of CAS Registry Number 797798-56: (8*7)+(7*9)+(6*7)+(5*7)+(4*9)+(3*8)+(2*5)+(1*6)=272 272 % 10 = 2 So 797798-56-2 is a valid CAS Registry Number.