280309 has 4 divisors (see below), whose sum is σ = 285120. Its totient is φ = 275500.

The previous prime is 280303. The next prime is 280321. The reversal of 280309 is 903082.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 903082 = 2 ⋅451541.

It is a cyclic number.

It is not a de Polignac number, because 280309 - 2⁵ = 280277 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 14.

It is a self number, because there is not a number n which added to its sum of digits gives 280309.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (280303) 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, 2317 + ... + 2434.

It is an arithmetic number, because the mean of its divisors is an integer number (71280).

2²⁸⁰³⁰⁹ is an apocalyptic number.

It is an amenable number.

280309 is a deficient number, since it is larger than the sum of its proper divisors (4811).

280309 is an equidigital number, since it uses as much as digits as its factorization.

280309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4810.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 280309 is about 529.4421592582. The cubic root of 280309 is about 65.4453830586.

The spelling of 280309 in words is "two hundred eighty thousand, three hundred nine".