The CAS Registry Mumber 75784-67-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,5,7,8 and 4 respectively; the second part has 2 digits, 6 and 7 respectively. Calculate Digit Verification of CAS Registry Number 75784-67: (7*7)+(6*5)+(5*7)+(4*8)+(3*4)+(2*6)+(1*7)=177 177 % 10 = 7 So 75784-67-7 is a valid CAS Registry Number.