400556021 has 4 divisors (see below), whose sum is σ = 400600332. Its totient is φ = 400511712.

The previous prime is 400555993. The next prime is 400556027. The reversal of 400556021 is 120655004.

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 can be written as a sum of positive squares in 2 ways, for example, as 66178225 + 334377796 = 8135^2 + 18286^2 .

It is a cyclic number.

It is not a de Polignac number, because 400556021 - 2⁶ = 400555957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400556027) 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, 3176 + ... + 28481.

It is an arithmetic number, because the mean of its divisors is an integer number (100150083).

Almost surely, 2^400556021 is an apocalyptic number.

It is an amenable number.

400556021 is a deficient number, since it is larger than the sum of its proper divisors (44311).

400556021 is a wasteful number, since it uses less digits than its factorization.

400556021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44310.

The product of its (nonzero) digits is 1200, while the sum is 23.

The square root of 400556021 is about 20013.8956977396. The cubic root of 400556021 is about 737.1475414752.

The spelling of 400556021 in words is "four hundred million, five hundred fifty-six thousand, twenty-one".