684173821645 has 4 divisors (see below), whose sum is σ = 821008585980. Its totient is φ = 547339057312.

The previous prime is 684173821627. The next prime is 684173821651. The reversal of 684173821645 is 546128371486.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 132906180969 + 551267640676 = 364563^2 + 742474^2 .

It is a cyclic number.

It is not a de Polignac number, because 684173821645 - 2²³ = 684165433037 is a prime.

It is a super-3 number, since 3×684173821645³ (a number of 36 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68417382160 + ... + 68417382169.

It is an arithmetic number, because the mean of its divisors is an integer number (205252146495).

Almost surely, 2^684173821645 is an apocalyptic number.

It is an amenable number.

684173821645 is a deficient number, since it is larger than the sum of its proper divisors (136834764335).

684173821645 is a wasteful number, since it uses less digits than its factorization.

684173821645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136834764334.

The product of its digits is 7741440, while the sum is 55.

The spelling of 684173821645 in words is "six hundred eighty-four billion, one hundred seventy-three million, eight hundred twenty-one thousand, six hundred forty-five".