404640 has 72 divisors (see below), whose sum is σ = 1385748. Its totient is φ = 107520.

The previous prime is 404597. The next prime is 404671. The reversal of 404640 is 46404.

It can be written as a sum of positive squares in 2 ways, for example, as 404496 + 144 = 636^2 + 12^2 .

It is a tau number, because it is divible by the number of its divisors (72).

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

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

404640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 1300 + ... + 1580.

2⁴⁰⁴⁶⁴⁰ is an apocalyptic number.

404640 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 404640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (692874).

404640 is an abundant number, since it is smaller than the sum of its proper divisors (981108).

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

404640 is a wasteful number, since it uses less digits than its factorization.

404640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 302 (or 291 counting only the distinct ones).

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

The square root of 404640 is about 636.1131974735. The cubic root of 404640 is about 73.9644338462.

The spelling of 404640 in words is "four hundred four thousand, six hundred forty".