21715853769 has 9 divisors (see below), whose sum is σ = 31367982919. Its totient is φ = 14476941120.

The previous prime is 21715853743. The next prime is 21715853791. The reversal of 21715853769 is 96735851712.

The square root of 21715853769 is 147363.

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

21715853769 is a `hidden beast` number, since 21 + 7 + 1 + 585 + 37 + 6 + 9 = 666.

It can be written as a sum of positive squares in only one way, i.e., 1324013769 + 20391840000 = 36387^2 + 142800^2 .

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

It is not a de Polignac number, because 21715853769 - 2¹⁷ = 21715722697 is a prime.

It is a super-2 number, since 2×21715853769² (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 (21715853869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 417529 + ... + 466649.

Almost surely, 2^21715853769 is an apocalyptic number.

21715853769 is the 147363-rd square number.

21715853769 is the 73682-nd centered octagonal number.

It is an amenable number.

21715853769 is a deficient number, since it is larger than the sum of its proper divisors (9652129150).

21715853769 is an frugal number, since it uses more digits than its factorization.

21715853769 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98248 (or 49124 counting only the distinct ones).

The product of its digits is 3175200, while the sum is 54.

The spelling of 21715853769 in words is "twenty-one billion, seven hundred fifteen million, eight hundred fifty-three thousand, seven hundred sixty-nine".