The CAS Registry Mumber 1743-37-9 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 1,7,4 and 3 respectively; the second part has 2 digits, 3 and 7 respectively. Calculate Digit Verification of CAS Registry Number 1743-37: (6*1)+(5*7)+(4*4)+(3*3)+(2*3)+(1*7)=79 79 % 10 = 9 So 1743-37-9 is a valid CAS Registry Number.