278545 has 16 divisors (see below), whose sum is σ = 369360. Its totient is φ = 200704.

The previous prime is 278543. The next prime is 278549. The reversal of 278545 is 545872.

278545 is nontrivially palindromic in base 2 and base 4.

It can be written as a sum of positive squares in 8 ways, for example, as 15376 + 263169 = 124^2 + 513^2 .

It is a 3-Lehmer number, since φ(278545) divides (278545-1)³.

It is a cyclic number.

It is a Carmichael number.

It is not a de Polignac number, because 278545 - 2¹ = 278543 is a prime.

It is a d-powerful number, because it can be written as 2⁷ + 7 + 5⁴ + 8⁶ + 4² + 5⁶ .

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

278545 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (278543) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2409 + ... + 2521.

It is an arithmetic number, because the mean of its divisors is an integer number (23085).

It is a Poulet number, since it divides 2²⁷⁸⁵⁴⁴-1.

2²⁷⁸⁵⁴⁵ is an apocalyptic number.

It is an amenable number.

278545 is a deficient number, since it is larger than the sum of its proper divisors (90815).

278545 is a wasteful number, since it uses less digits than its factorization.

278545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164.

The product of its digits is 11200, while the sum is 31.

The square root of 278545 is about 527.7736257147. The cubic root of 278545 is about 65.3078102674.

The spelling of 278545 in words is "two hundred seventy-eight thousand, five hundred forty-five".