278821 has 4 divisors (see below), whose sum is σ = 281632. Its totient is φ = 276012.

The previous prime is 278819. The next prime is 278827. The reversal of 278821 is 128872.

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.

It is a cyclic number.

It is not a de Polignac number, because 278821 - 2¹ = 278819 is a prime.

It is a Duffinian number.

278821 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 278821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (278827) 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, 1251 + ... + 1456.

It is an arithmetic number, because the mean of its divisors is an integer number (70408).

2²⁷⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

278821 is a deficient number, since it is larger than the sum of its proper divisors (2811).

278821 is a wasteful number, since it uses less digits than its factorization.

278821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2810.

The product of its digits is 1792, while the sum is 28.

The square root of 278821 is about 528.0350367163. The cubic root of 278821 is about 65.3293735163.

It can be divided in two parts, 2788 and 21, that added together give a square (2809 = 53²).

The spelling of 278821 in words is "two hundred seventy-eight thousand, eight hundred twenty-one".