400840 has 32 divisors (see below), whose sum is σ = 984960. Its totient is φ = 145600.

The previous prime is 400837. The next prime is 400849. The reversal of 400840 is 48004.

It is not an unprimeable number, because it can be changed into a prime (400849) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16 + ... + 895.

It is an arithmetic number, because the mean of its divisors is an integer number (30780).

2⁴⁰⁰⁸⁴⁰ is an apocalyptic number.

400840 is a gapful number since it is divisible by the number (40) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 400840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (492480).

400840 is an abundant number, since it is smaller than the sum of its proper divisors (584120).

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

400840 is a wasteful number, since it uses less digits than its factorization.

400840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 933 (or 929 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 400840 is about 633.1192620668. The cubic root of 400840 is about 73.7321703523.

Adding to 400840 its reverse (48004), we get a palindrome (448844).

Subtracting from 400840 its reverse (48004), we obtain a square (352836 = 594²).

The spelling of 400840 in words is "four hundred thousand, eight hundred forty".