The greatest whole number that rounds to 7,400 would be 7,399. This is because there is no number that is larger than 7,399 that would round up to 7,400, since 7,400 is the next number.
The least whole number that rounds to 7,400 would be 7,401. This is because there is no number that is less than 7,401 that would round up to 7,400, since 7,400 is the next number.