Answer:
The safety of a password depends on various factors, including its complexity, length, and the characters used. In general, a longer password is safer.
1. Password made up of five letters: Assuming only lowercase letters are used (26 possibilities for each character), there are 26^5 (11881376) different combinations.
2. A seven-digit number: Assuming only digits (0-9) are used for each digit, there are 10^7 (10,000,000) different combinations.
Based on the number of different combinations, a seven-digit number is safer as it has more potential combinations than a five-letter password. However, for a truly secure password, you should also consider using a mix of uppercase letters, lowercase letters, digits, and special characters, and make it longer.
Remember that safety also depends on factors like the encryption strength of the system using the password and whether it can resist various forms of attacks, including brute force and dictionary attacks.