681761645 has 6 divisors (see below), whose sum is σ = 818184042. Its totient is φ = 545362608.

The previous prime is 681761623. The next prime is 681761683. The reversal of 681761645 is 546167186.

It can be written as a sum of positive squares in 3 ways, for example, as 293711044 + 388050601 = 17138^2 + 19699^2 .

It is not a de Polignac number, because 681761645 - 2⁶ = 681761581 is a prime.

It is a super-3 number, since 3×681761645³ (a number of 27 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 681761596 and 681761605.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 52547 + ... + 64223.

It is an arithmetic number, because the mean of its divisors is an integer number (136364007).

Almost surely, 2^681761645 is an apocalyptic number.

It is an amenable number.

681761645 is a deficient number, since it is larger than the sum of its proper divisors (136422397).

681761645 is an frugal number, since it uses more digits than its factorization.

681761645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23359 (or 11682 counting only the distinct ones).

The product of its digits is 241920, while the sum is 44.

The square root of 681761645 is about 26110.5657732650. The cubic root of 681761645 is about 880.1246573579.

The spelling of 681761645 in words is "six hundred eighty-one million, seven hundred sixty-one thousand, six hundred forty-five".