278909 has 2 divisors, whose sum is σ = 278910. Its totient is φ = 278908.

The previous prime is 278903. The next prime is 278911. The reversal of 278909 is 909872.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 240100 + 38809 = 490^2 + 197^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-278909 is a prime.

Together with 278911, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (278903) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 139454 + 139455.

It is an arithmetic number, because the mean of its divisors is an integer number (139455).

2²⁷⁸⁹⁰⁹ is an apocalyptic number.

It is an amenable number.

278909 is a deficient number, since it is larger than the sum of its proper divisors (1).

278909 is an equidigital number, since it uses as much as digits as its factorization.

278909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 35.

The square root of 278909 is about 528.1183579464. The cubic root of 278909 is about 65.3362457631.

The spelling of 278909 in words is "two hundred seventy-eight thousand, nine hundred nine".