400640 has 36 divisors (see below), whose sum is σ = 962724. Its totient is φ = 159744.

The previous prime is 400619. The next prime is 400643. The reversal of 400640 is 46004.

It is a happy number.

400640 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 50176 + 350464 = 224^2 + 592^2 .

It is a hoax number, since the sum of its digits (14) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (400643) 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, 1124 + ... + 1436.

2⁴⁰⁰⁶⁴⁰ is an apocalyptic number.

400640 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 400640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (481362).

400640 is an abundant number, since it is smaller than the sum of its proper divisors (562084).

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

400640 is an equidigital number, since it uses as much as digits as its factorization.

400640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 334 (or 320 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 400640 is about 632.9612942353. The cubic root of 400640 is about 73.7199053694.

Adding to 400640 its reverse (46004), we get a palindrome (446644).

The spelling of 400640 in words is "four hundred thousand, six hundred forty".