400639 has 4 divisors (see below), whose sum is σ = 424224. Its totient is φ = 377056.

The previous prime is 400619. The next prime is 400643. The reversal of 400639 is 936004.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 400639 - 2⁵ = 400607 is a prime.

It is a Duffinian number.

It is a zygodrome in base 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400619) 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, 11767 + ... + 11800.

It is an arithmetic number, because the mean of its divisors is an integer number (106056).

2⁴⁰⁰⁶³⁹ is an apocalyptic number.

400639 is a deficient number, since it is larger than the sum of its proper divisors (23585).

400639 is a wasteful number, since it uses less digits than its factorization.

400639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23584.

The product of its (nonzero) digits is 648, while the sum is 22.

The square root of 400639 is about 632.9605042971. The cubic root of 400639 is about 73.7198440342.

The spelling of 400639 in words is "four hundred thousand, six hundred thirty-nine".