278809 has 2 divisors, whose sum is σ = 278810. Its totient is φ = 278808.

The previous prime is 278807. The next prime is 278813. The reversal of 278809 is 908872.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 278784 + 25 = 528^2 + 5^2 .

It is a cyclic number.

It is not a de Polignac number, because 278809 - 2¹ = 278807 is a prime.

Together with 278807, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (278801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 139404 + 139405.

It is an arithmetic number, because the mean of its divisors is an integer number (139405).

2²⁷⁸⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

278809 is a deficient number, since it is larger than the sum of its proper divisors (1).

278809 is an equidigital number, since it uses as much as digits as its factorization.

278809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 34.

The square root of 278809 is about 528.0236737117. The cubic root of 278809 is about 65.3284362797.

It can be divided in two parts, 27880 and 9, that added together give a square (27889 = 167²).

The spelling of 278809 in words is "two hundred seventy-eight thousand, eight hundred nine".