684905 has 16 divisors (see below), whose sum is σ = 910224. Its totient is φ = 491520.

The previous prime is 684889. The next prime is 684923. The reversal of 684905 is 509486.

It can be written as a sum of positive squares in 8 ways, for example, as 32041 + 652864 = 179^2 + 808^2 .

It is not a de Polignac number, because 684905 - 2⁴ = 684889 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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, 2537 + ... + 2793.

It is an arithmetic number, because the mean of its divisors is an integer number (56889).

2⁶⁸⁴⁹⁰⁵ is an apocalyptic number.

684905 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

684905 is a deficient number, since it is larger than the sum of its proper divisors (225319).

684905 is a wasteful number, since it uses less digits than its factorization.

684905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 316.

The product of its (nonzero) digits is 8640, while the sum is 32.

The square root of 684905 is about 827.5898742735. The cubic root of 684905 is about 88.1475228718.

The spelling of 684905 in words is "six hundred eighty-four thousand, nine hundred five".