684440 has 32 divisors (see below), whose sum is σ = 1568160. Its totient is φ = 268800.

The previous prime is 684433. The next prime is 684443. The reversal of 684440 is 44486.

It is a super-2 number, since 2×684440² = 936916227200, which contains 22 as substring.

It is a Smith number, since the sum of its digits (26) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (684443) 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, 2720 + ... + 2960.

It is an arithmetic number, because the mean of its divisors is an integer number (49005).

2⁶⁸⁴⁴⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 684440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (784080).

684440 is an abundant number, since it is smaller than the sum of its proper divisors (883720).

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

684440 is a wasteful number, since it uses less digits than its factorization.

684440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323 (or 319 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 26.

The square root of 684440 is about 827.3088903185. The cubic root of 684440 is about 88.1275697991.

The spelling of 684440 in words is "six hundred eighty-four thousand, four hundred forty".