405821235681 has 27 divisors (see below), whose sum is σ = 622745953843. Its totient is φ = 254612546880.

The previous prime is 405821235653. The next prime is 405821235689. The reversal of 405821235681 is 186532128504.

The square root of 405821235681 is 637041.

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

405821235681 is a `hidden beast` number, since 4 + 0 + 5 + 8 + 212 + 356 + 81 = 666.

It can be written as a sum of positive squares in only one way, i.e., 315950789025 + 89870446656 = 562095^2 + 299784^2 .

It is not a de Polignac number, because 405821235681 - 2⁵ = 405821235649 is a prime.

It is a super-2 number, since 2×405821235681² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (405821235689) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 32482846 + ... + 32495336.

Almost surely, 2^405821235681 is an apocalyptic number.

405821235681 is the 637041-st square number.

405821235681 is the 318521-st centered octagonal number.

It is an amenable number.

405821235681 is a deficient number, since it is larger than the sum of its proper divisors (216924718162).

405821235681 is an frugal number, since it uses more digits than its factorization.

405821235681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25022 (or 12511 counting only the distinct ones).

The product of its (nonzero) digits is 460800, while the sum is 45.

The spelling of 405821235681 in words is "four hundred five billion, eight hundred twenty-one million, two hundred thirty-five thousand, six hundred eighty-one".