The CAS Registry Mumber 74378-47-5 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 7,4,3,7 and 8 respectively; the second part has 2 digits, 4 and 7 respectively. Calculate Digit Verification of CAS Registry Number 74378-47: (7*7)+(6*4)+(5*3)+(4*7)+(3*8)+(2*4)+(1*7)=155 155 % 10 = 5 So 74378-47-5 is a valid CAS Registry Number.