21971634386881 has 27 divisors (see below), whose sum is σ = 22372540083369. Its totient is φ = 21577898230272.

The previous prime is 21971634386851. The next prime is 21971634386909. The reversal of 21971634386881 is 18868343617912.

The square root of 21971634386881 is 4687391.

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

It can be written as a sum of positive squares in 4 ways, for example, as 9266088200625 + 12705546186256 = 3044025^2 + 3564484^2 .

It is not a de Polignac number, because 21971634386881 - 2⁹ = 21971634386369 is a prime.

It is a super-2 number, since 2×21971634386881² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21971634386831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 113842665121 + ... + 113842665313.

Almost surely, 2^{21971634386881} is an apocalyptic number.

21971634386881 is the 4687391-st square number.

21971634386881 is the 2343696-th centered octagonal number.

It is an amenable number.

21971634386881 is a deficient number, since it is larger than the sum of its proper divisors (400905696488).

21971634386881 is an frugal number, since it uses more digits than its factorization.

21971634386881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1010 (or 505 counting only the distinct ones).

The product of its digits is 83607552, while the sum is 67.

The spelling of 21971634386881 in words is "twenty-one trillion, nine hundred seventy-one billion, six hundred thirty-four million, three hundred eighty-six thousand, eight hundred eighty-one".