400390400 has 108 divisors (see below), whose sum is σ = 1005776772. Its totient is φ = 157777920.

The previous prime is 400390373. The next prime is 400390421. The reversal of 400390400 is 4093004.

It can be written as a sum of positive squares in 6 ways, for example, as 8667136 + 391723264 = 2944^2 + 19792^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 466772 + ... + 467628.

Almost surely, 2^400390400 is an apocalyptic number.

400390400 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 400390400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (502888386).

400390400 is an abundant number, since it is smaller than the sum of its proper divisors (605386372).

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

400390400 is an equidigital number, since it uses as much as digits as its factorization.

400390400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 956 (or 937 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 20.

The square root of 400390400 is about 20009.7576197214. The cubic root of 400390400 is about 737.0459294350.

The spelling of 400390400 in words is "four hundred million, three hundred ninety thousand, four hundred".