861724180681 has 45 divisors (see below), whose sum is σ = 1096308583155. Its totient is φ = 675053215200.

The previous prime is 861724180637. The next prime is 861724180697. The reversal of 861724180681 is 186081427168.

The square root of 861724180681 is 928291.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 7 ways, for example, as 12996025 + 861711184656 = 3605^2 + 928284^2 .

It is not a de Polignac number, because 861724180681 - 2²¹ = 861722083529 is a prime.

It is a super-2 number, since 2×861724180681² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (861724180631) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 8531922531 + ... + 8531922631.

It is an arithmetic number, because the mean of its divisors is an integer number (24362412959).

Almost surely, 2^861724180681 is an apocalyptic number.

861724180681 is the 928291-st square number.

861724180681 is the 464146-th centered octagonal number.

It is an amenable number.

861724180681 is a deficient number, since it is larger than the sum of its proper divisors (234584402474).

861724180681 is an frugal number, since it uses more digits than its factorization.

861724180681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 444 (or 121 counting only the distinct ones).

The product of its (nonzero) digits is 1032192, while the sum is 52.

The spelling of 861724180681 in words is "eight hundred sixty-one billion, seven hundred twenty-four million, one hundred eighty thousand, six hundred eighty-one".