280505 has 4 divisors (see below), whose sum is σ = 336612. Its totient is φ = 224400.

The previous prime is 280499. The next prime is 280507. The reversal of 280505 is 505082.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 505082 = 2 ⋅252541.

It can be written as a sum of positive squares in 2 ways, for example, as 141376 + 139129 = 376^2 + 373^2 .

It is not a de Polignac number, because 280505 - 2⁸ = 280249 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 14.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 280505.

It is not an unprimeable number, because it can be changed into a prime (280507) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 28046 + ... + 28055.

It is an arithmetic number, because the mean of its divisors is an integer number (84153).

2²⁸⁰⁵⁰⁵ is an apocalyptic number.

It is an amenable number.

280505 is a deficient number, since it is larger than the sum of its proper divisors (56107).

280505 is an equidigital number, since it uses as much as digits as its factorization.

280505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56106.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 280505 is about 529.6272273968. The cubic root of 280505 is about 65.4606332605.

Adding to 280505 its reverse (505082), we get a palindrome (785587).

The spelling of 280505 in words is "two hundred eighty thousand, five hundred five".