369 (number) explained

369 (three hundred [and] sixty-nine) is the natural number following 368 and preceding 370.

In mathematics

369 is the magic constant of the 9 × 9 magic square^{[1] [2]} and the n-Queens Problem for n = 9.^[2]

There are 369 free octominoes (polyominoes of order 8).^{[3] [4]}

369 is a Ruth-Aaron Pair with 370. The sums of their prime factors are equivalent.^[5]

Notes and References

1. Book: Kraitchik, M. Mathematical Recreations. Norton. New York. 1942. 142–192. Magic Squares.
2. Sequence A006003 in OEIS.
3. Redelmeier . D. Hugh . 1981 . Counting polyominoes: yet another attack . Discrete Mathematics . 36 . 2 . 191–203 . 10.1016/0012-365X(81)90237-5. free .
4. Sequence A000105 in OEIS.
5. Web site: Ruth-Aaron Pair. mathworld.wolfram.com.