The CAS Registry Mumber 74786-23-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,7,8 and 6 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 74786-23: (7*7)+(6*4)+(5*7)+(4*8)+(3*6)+(2*2)+(1*3)=165 165 % 10 = 5 So 74786-23-5 is a valid CAS Registry Number.