The CAS Registry Mumber 75804-79-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,8,0 and 4 respectively; the second part has 2 digits, 7 and 9 respectively. Calculate Digit Verification of CAS Registry Number 75804-79: (7*7)+(6*5)+(5*8)+(4*0)+(3*4)+(2*7)+(1*9)=154 154 % 10 = 4 So 75804-79-4 is a valid CAS Registry Number.