507

507 = 3 x 13 x 13.

507 is a divisor of 22³ - 1.

507 is 13323 in base 4 and 1323 in base 7.

507 is the lesser of two consecutive numbers (507 and 508) each divisible by a square.

The square of 507 contains exactly six different digits: 507² = 257049.

507 is the number of rooted ternary trees with 10 vertices.

Source: What's Special About This Number?