21481806713409 has 189 divisors, whose sum is σ = 37953921650547. Its totient is φ = 12117640627008.

The previous prime is 21481806713387. The next prime is 21481806713417. The reversal of 21481806713409 is 90431760818412.

The square root of 21481806713409 is 4634847.

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

21481806713409 is a `hidden beast` number, since 2 + 1 + 48 + 180 + 6 + 7 + 13 + 409 = 666.

It can be written as a sum of positive squares in only one way, i.e., 12618515585025 + 8863291128384 = 3552255^2 + 2977128^2 .

It is a tau number, because it is divible by the number of its divisors (189).

It is not a de Polignac number, because 21481806713409 - 2¹⁵ = 21481806680641 is a prime.

It is a super-2 number, since 2×21481806713409² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21481806713489) by changing a digit.

It is a polite number, since it can be written in 188 ways as a sum of consecutive naturals, for example, 120010093282 + ... + 120010093460.

Almost surely, 2^{21481806713409} is an apocalyptic number.

21481806713409 is the 4634847-th square number.

21481806713409 is the 2317424-th centered octagonal number.

It is an amenable number.

21481806713409 is a deficient number, since it is larger than the sum of its proper divisors (16472114937138).

21481806713409 is an frugal number, since it uses more digits than its factorization.

21481806713409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 664 (or 326 counting only the distinct ones).

The product of its (nonzero) digits is 2322432, while the sum is 54.

The spelling of 21481806713409 in words is "twenty-one trillion, four hundred eighty-one billion, eight hundred six million, seven hundred thirteen thousand, four hundred nine".