280905 has 16 divisors (see below), whose sum is σ = 458304. Its totient is φ = 146880.

The previous prime is 280897. The next prime is 280909. The reversal of 280905 is 509082.

It is not a de Polignac number, because 280905 - 2³ = 280897 is a prime.

It is a plaindrome in base 12.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 280905.

It is not an unprimeable number, because it can be changed into a prime (280909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 762 + ... + 1068.

It is an arithmetic number, because the mean of its divisors is an integer number (28644).

2²⁸⁰⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

280905 is a deficient number, since it is larger than the sum of its proper divisors (177399).

280905 is a wasteful number, since it uses less digits than its factorization.

280905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 376.

The product of its (nonzero) digits is 720, while the sum is 24.

The square root of 280905 is about 530.0047169601. The cubic root of 280905 is about 65.4917340928.

Adding to 280905 its product of nonzero digits (720), we get a triangular number (281625 = T₇₅₀).

Adding to 280905 its reverse (509082), we get a palindrome (789987).

The spelling of 280905 in words is "two hundred eighty thousand, nine hundred five".