684398665 has 16 divisors (see below), whose sum is σ = 870332688. Its totient is φ = 514871296.

The previous prime is 684398653. The next prime is 684398681. The reversal of 684398665 is 566893486.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 199826496 + 484572169 = 14136^2 + 22013^2 .

It is a cyclic number.

It is not a de Polignac number, because 684398665 - 2⁵ = 684398633 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 124209 + ... + 129601.

It is an arithmetic number, because the mean of its divisors is an integer number (54395793).

Almost surely, 2^684398665 is an apocalyptic number.

It is an amenable number.

684398665 is a deficient number, since it is larger than the sum of its proper divisors (185934023).

684398665 is a wasteful number, since it uses less digits than its factorization.

684398665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6908.

The product of its digits is 7464960, while the sum is 55.

The square root of 684398665 is about 26161.0142196361. The cubic root of 684398665 is about 881.2579568384.

The spelling of 684398665 in words is "six hundred eighty-four million, three hundred ninety-eight thousand, six hundred sixty-five".