21167631081 has 9 divisors (see below), whose sum is σ = 30576097591. Its totient is φ = 14111463072.

The previous prime is 21167631071. The next prime is 21167631083. The reversal of 21167631081 is 18013676112.

The square root of 21167631081 is 145491.

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

21167631081 is a `hidden beast` number, since 2 + 1 + 16 + 7 + 631 + 0 + 8 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 3322946025 + 17844685056 = 57645^2 + 133584^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 21167631081 - 2¹⁵ = 21167598313 is a prime.

It is a super-2 number, since 2×21167631081² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21167631083) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 412225 + ... + 460721.

Almost surely, 2^21167631081 is an apocalyptic number.

21167631081 is the 145491-st square number.

21167631081 is the 72746-th centered octagonal number.

It is an amenable number.

21167631081 is a deficient number, since it is larger than the sum of its proper divisors (9408466510).

21167631081 is an frugal number, since it uses more digits than its factorization.

21167631081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97000 (or 48500 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

Multiplying 21167631081 by its sum of digits (36), we get a square (762034718916 = 872946²).

The spelling of 21167631081 in words is "twenty-one billion, one hundred sixty-seven million, six hundred thirty-one thousand, eighty-one".