664440 has 96 divisors (see below), whose sum is σ = 2339280. Its totient is φ = 150528.

The previous prime is 664427. The next prime is 664441. The reversal of 664440 is 44466.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 664440.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664441) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5824 + ... + 5936.

2⁶⁶⁴⁴⁴⁰ is an apocalyptic number.

664440 is a gapful number since it is divisible by the number (60) 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 664440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1169640).

664440 is an abundant number, since it is smaller than the sum of its proper divisors (1674840).

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

664440 is a wasteful number, since it uses less digits than its factorization.

664440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 664440 is about 815.1318911685. The cubic root of 664440 is about 87.2606793659.

It can be divided in two parts, 6 and 64440, that added together give a palindrome (64446).

The spelling of 664440 in words is "six hundred sixty-four thousand, four hundred forty".