400005821 has 4 divisors (see below), whose sum is σ = 400153152. Its totient is φ = 399858492.

The previous prime is 400005757. The next prime is 400005863. The reversal of 400005821 is 128500004.

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 400005821 - 2⁶ = 400005757 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 400005793 and 400005802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400005871) 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, 69515 + ... + 75048.

It is an arithmetic number, because the mean of its divisors is an integer number (100038288).

Almost surely, 2^400005821 is an apocalyptic number.

It is an amenable number.

400005821 is a deficient number, since it is larger than the sum of its proper divisors (147331).

400005821 is a wasteful number, since it uses less digits than its factorization.

400005821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147330.

The product of its (nonzero) digits is 320, while the sum is 20.

The square root of 400005821 is about 20000.1455244706. The cubic root of 400005821 is about 736.8098738353.

Adding to 400005821 its reverse (128500004), we get a palindrome (528505825).

The spelling of 400005821 in words is "four hundred million, five thousand, eight hundred twenty-one".