280805 has 16 divisors (see below), whose sum is σ = 393984. Its totient is φ = 188160.

The previous prime is 280771. The next prime is 280811. The reversal of 280805 is 508082.

280805 = T₆ + T₇ + ... + T₁₁₈.

280805 = 72² + 73² + ... + 106².

It is not a de Polignac number, because 280805 - 2⁸ = 280549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 280805.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2429 + ... + 2541.

It is an arithmetic number, because the mean of its divisors is an integer number (24624).

2²⁸⁰⁸⁰⁵ is an apocalyptic number.

It is an amenable number.

280805 is a deficient number, since it is larger than the sum of its proper divisors (113179).

280805 is a wasteful number, since it uses less digits than its factorization.

280805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 280805 is about 529.9103697796. The cubic root of 280805 is about 65.4839616540.

Adding to 280805 its reverse (508082), we get a palindrome (788887).

The spelling of 280805 in words is "two hundred eighty thousand, eight hundred five".