21744156681 has 81 divisors (see below), whose sum is σ = 36075586599. Its totient is φ = 12613053024.

The previous prime is 21744156659. The next prime is 21744156739. The reversal of 21744156681 is 18665144712.

The square root of 21744156681 is 147459.

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

21744156681 is a `hidden beast` number, since 2 + 1 + 7 + 4 + 4 + 1 + 566 + 81 = 666.

It can be written as a sum of positive squares in only one way, i.e., 3216591225 + 18527565456 = 56715^2 + 136116^2 .

It is not a de Polignac number, because 21744156681 - 2¹⁵ = 21744123913 is a prime.

It is a super-2 number, since 2×21744156681² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21744156601) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 109267020 + ... + 109267218.

Almost surely, 2^21744156681 is an apocalyptic number.

21744156681 is the 147459-th square number.

21744156681 is the 73730-th centered octagonal number.

It is an amenable number.

21744156681 is a deficient number, since it is larger than the sum of its proper divisors (14331429918).

21744156681 is a wasteful number, since it uses less digits than its factorization.

21744156681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 468 (or 234 counting only the distinct ones).

The product of its digits is 322560, while the sum is 45.

The spelling of 21744156681 in words is "twenty-one billion, seven hundred forty-four million, one hundred fifty-six thousand, six hundred eighty-one".