2005

2005 = 5 x 401.

2005 is a semiprime that is the sum of four successive semiprimes (A158339).

2005 = 1 + 2 x 3¹ + 3 x 3² + 4 x 3³ + 5 x 3⁴ + 6 x 3⁵ (A113531).

2005 has two representations as a sum of two squares: 2005 = 18² + 41² = 22² + 39².

2005 is the hypotenuse of two primitive Pythagorean triples: 2005² = 1037² + 1716² = 1357² + 1476².

2005 is a divisor of 98⁸ - 1.

2005 and the square of 2005 use only the digits 0, 2, 4, and 5 (A136897).

2005 is considered a vertically symmetric number (A053701).

Source: On-Line Encyclopedia of Integer Sequences