The CAS Registry Mumber 1796-04-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,7,9 and 6 respectively; the second part has 2 digits, 0 and 4 respectively. Calculate Digit Verification of CAS Registry Number 1796-04: (6*1)+(5*7)+(4*9)+(3*6)+(2*0)+(1*4)=99 99 % 10 = 9 So 1796-04-9 is a valid CAS Registry Number.