400891 has 4 divisors (see below), whose sum is σ = 402192. Its totient is φ = 399592.

The previous prime is 400871. The next prime is 400903. The reversal of 400891 is 198004.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 400891 - 2⁵ = 400859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (400871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105 + ... + 901.

It is an arithmetic number, because the mean of its divisors is an integer number (100548).

2⁴⁰⁰⁸⁹¹ is an apocalyptic number.

400891 is a deficient number, since it is larger than the sum of its proper divisors (1301).

400891 is an equidigital number, since it uses as much as digits as its factorization.

400891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1300.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 400891 is about 633.1595375575. The cubic root of 400891 is about 73.7352972702.

Adding to 400891 its reverse (198004), we get a palindrome (598895).

The spelling of 400891 in words is "four hundred thousand, eight hundred ninety-one".