684978 has 32 divisors (see below), whose sum is σ = 1603584. Its totient is φ = 190992.

The previous prime is 684977. The next prime is 684989. The reversal of 684978 is 879486.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is not an unprimeable number, because it can be changed into a prime (684973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1801 + ... + 2147.

It is an arithmetic number, because the mean of its divisors is an integer number (50112).

2⁶⁸⁴⁹⁷⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 684978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (801792).

684978 is an abundant number, since it is smaller than the sum of its proper divisors (918606).

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

684978 is a wasteful number, since it uses less digits than its factorization.

684978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 406.

The product of its digits is 96768, while the sum is 42.

The square root of 684978 is about 827.6339770696. The cubic root of 684978 is about 88.1506544694.

The spelling of 684978 in words is "six hundred eighty-four thousand, nine hundred seventy-eight".