### Today’s Puzzle:

This star puzzle is one thing I’m doing to commemorate this historic day when Joe Biden is inaugurated as the 46th President of the United States and Kamala Harris is inaugurated as Vice President! He will be the oldest person to become President, having previously served 36 years in the Senate and 8 years as Vice President, and she will be the first woman, the first African-American, and the first Asian-American Vice President. I wish them a beautiful day as they begin the hard work of uniting our country and finding solutions that benefit all of us.

The clues 10, 20, 30, and 40 have two common factors that might work for this mystery level puzzle. However, the other factors that go with one of those two choices will completely eliminate every possible factor pair for clue 4. That means you need to go with the other possibility.

### Factors of 1579:

- 1579 is a prime number.
- Prime factorization: 1579 is prime.
- 1579 has no exponents greater than 1 in its prime factorization, so √1579 cannot be simplified.
- The exponent in the prime factorization is 1. Adding one to that exponent we get (1 + 1) = 2. Therefore 1579 has exactly 2 factors.
- The factors of 1579 are outlined with their factor pair partners in the graphic below.

**How do we know that 1579 is a prime number?** If 1579 were not a prime number, then it would be divisible by at least one prime number less than or equal to √1579. Since 1579 cannot be divided evenly by 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, or 37, we know that 1579 is a prime number.

### More About the Number 1579:

1579 is the sum of two consecutive numbers:

789 + 790 = 1579.

1579 is also the difference of two consecutive squares:

790² – 789² = 1579.

**1579**, 9**1579**9, 99**1579**99, 999**1579**999, and 9999**1579**9999 are all prime numbers! Thanks to OEIS.org for alerting me to that fabulous fact!