The CAS Registry Mumber 74728-37-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,7,2 and 8 respectively; the second part has 2 digits, 3 and 7 respectively. Calculate Digit Verification of CAS Registry Number 74728-37: (7*7)+(6*4)+(5*7)+(4*2)+(3*8)+(2*3)+(1*7)=153 153 % 10 = 3 So 74728-37-3 is a valid CAS Registry Number.