21705811481 has 4 divisors (see below), whose sum is σ = 21786502500. Its totient is φ = 21625120464.

The previous prime is 21705811469. The next prime is 21705811513. The reversal of 21705811481 is 18411850712.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8405955856 + 13299855625 = 91684^2 + 115325^2 .

It is a cyclic number.

It is not a de Polignac number, because 21705811481 - 2³⁴ = 4525942297 is a prime.

It is a super-2 number, since 2×21705811481² (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 (21705811411) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40345106 + ... + 40345643.

It is an arithmetic number, because the mean of its divisors is an integer number (5446625625).

Almost surely, 2^21705811481 is an apocalyptic number.

It is an amenable number.

21705811481 is a deficient number, since it is larger than the sum of its proper divisors (80691019).

21705811481 is an equidigital number, since it uses as much as digits as its factorization.

21705811481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80691018.

The product of its (nonzero) digits is 17920, while the sum is 38.

The spelling of 21705811481 in words is "twenty-one billion, seven hundred five million, eight hundred eleven thousand, four hundred eighty-one".