400644 has 36 divisors (see below), whose sum is σ = 1048320. Its totient is φ = 128880.

The previous prime is 400643. The next prime is 400651. The reversal of 400644 is 446004.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×400644² = 321031229472, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 400644.

It is not an unprimeable number, because it can be changed into a prime (400643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 937 + ... + 1295.

It is an arithmetic number, because the mean of its divisors is an integer number (29120).

2⁴⁰⁰⁶⁴⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 400644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (524160).

400644 is an abundant number, since it is smaller than the sum of its proper divisors (647676).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

400644 is a wasteful number, since it uses less digits than its factorization.

400644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 400 (or 395 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 400644 is about 632.9644539783. The cubic root of 400644 is about 73.7201507090.

Adding to 400644 its reverse (446004), we get a palindrome (846648).

The spelling of 400644 in words is "four hundred thousand, six hundred forty-four".