The CAS Registry Mumber 74372-77-3 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,3,7 and 2 respectively; the second part has 2 digits, 7 and 7 respectively. Calculate Digit Verification of CAS Registry Number 74372-77: (7*7)+(6*4)+(5*3)+(4*7)+(3*2)+(2*7)+(1*7)=143 143 % 10 = 3 So 74372-77-3 is a valid CAS Registry Number.