305

305 = 5 x 61.

305 is the smallest odd composite that is the average of two consecutive Fibonacci numbers (233 and 377).

305 has two representations as a sum of two squares: 305 = 4² + 17² = 7² + 16².

305 is the hypotenuse of two primitive Pythagorean triples: 305² = 136² + 273² = 207² + 224².

305 is a divisor of 11⁴ - 1.

305 is the fifth hexagonal prism number. A hexagonal prism number has the form (n + 1)(n² + 3n + 1).

305 is 614 is base 7 and 461 in base 8.

Source: Prime Curios!