278689 has 2 divisors, whose sum is σ = 278690. Its totient is φ = 278688.

The previous prime is 278687. The next prime is 278701. The reversal of 278689 is 986872.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 166464 + 112225 = 408^2 + 335^2 .

It is a cyclic number.

It is not a de Polignac number, because 278689 - 2¹ = 278687 is a prime.

Together with 278687, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (278687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 139344 + 139345.

It is an arithmetic number, because the mean of its divisors is an integer number (139345).

2²⁷⁸⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

278689 is a deficient number, since it is larger than the sum of its proper divisors (1).

278689 is an equidigital number, since it uses as much as digits as its factorization.

278689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 48384, while the sum is 40.

The square root of 278689 is about 527.9100302135. The cubic root of 278689 is about 65.3190624344.

The spelling of 278689 in words is "two hundred seventy-eight thousand, six hundred eighty-nine".