684840 has 64 divisors (see below), whose sum is σ = 2217600. Its totient is φ = 168192.

The previous prime is 684829. The next prime is 684841. The reversal of 684840 is 48486.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 684798 and 684807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (684841) by changing a digit.

684840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1341 + ... + 1779.

It is an arithmetic number, because the mean of its divisors is an integer number (34650).

2⁶⁸⁴⁸⁴⁰ is an apocalyptic number.

684840 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 684840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1108800).

684840 is an abundant number, since it is smaller than the sum of its proper divisors (1532760).

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

684840 is a wasteful number, since it uses less digits than its factorization.

684840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 466 (or 462 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 30.

The square root of 684840 is about 827.5506026824. The cubic root of 684840 is about 88.1447342757.

The spelling of 684840 in words is "six hundred eighty-four thousand, eight hundred forty".