The CAS Registry Mumber 73875-23-7 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,3,8,7 and 5 respectively; the second part has 2 digits, 2 and 3 respectively. Calculate Digit Verification of CAS Registry Number 73875-23: (7*7)+(6*3)+(5*8)+(4*7)+(3*5)+(2*2)+(1*3)=157 157 % 10 = 7 So 73875-23-7 is a valid CAS Registry Number.