21866855792401 has 3 divisors (see below), whose sum is σ = 21866860468603. Its totient is φ = 21866851116200.

The previous prime is 21866855792393. The next prime is 21866855792413. The reversal of 21866855792401 is 10429755866812.

The square root of 21866855792401 is 4676201.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 17101541430801 + 4765314361600 = 4135401^2 + 2182960^2 .

It is not a de Polignac number, because 21866855792401 - 2³ = 21866855792393 is a prime.

It is a super-2 number, since 2×21866855792401² (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 (21866855792461) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2338101 + ... + 7014301.

Almost surely, 2^{21866855792401} is an apocalyptic number.

21866855792401 is the 4676201-st square number.

21866855792401 is the 2338101-st centered octagonal number.

It is an amenable number.

21866855792401 is a deficient number, since it is larger than the sum of its proper divisors (4676202).

21866855792401 is an frugal number, since it uses more digits than its factorization.

21866855792401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9352402 (or 4676201 counting only the distinct ones).

The product of its (nonzero) digits is 58060800, while the sum is 64.

The spelling of 21866855792401 in words is "twenty-one trillion, eight hundred sixty-six billion, eight hundred fifty-five million, seven hundred ninety-two thousand, four hundred one".