21936868321 has 9 divisors (see below), whose sum is σ = 22551414291. Its totient is φ = 21338647992.

The previous prime is 21936868297. The next prime is 21936868351. The reversal of 21936868321 is 12386863912.

The square root of 21936868321 is 148111.

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

It can be written as a sum of positive squares in only one way, i.e., 19629411025 + 2307457296 = 140105^2 + 48036^2 .

It is not a de Polignac number, because 21936868321 - 2¹⁵ = 21936835553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21936868351) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 5478106 + ... + 5482108.

It is an arithmetic number, because the mean of its divisors is an integer number (2505712699).

Almost surely, 2^21936868321 is an apocalyptic number.

21936868321 is the 148111-st square number.

21936868321 is the 74056-th centered octagonal number.

It is an amenable number.

21936868321 is a deficient number, since it is larger than the sum of its proper divisors (614545970).

21936868321 is an frugal number, since it uses more digits than its factorization.

21936868321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8080 (or 4040 counting only the distinct ones).

The product of its digits is 746496, while the sum is 49.

Multiplying 21936868321 by its sum of digits (49), we get a square (1074906547729 = 1036777²).

The spelling of 21936868321 in words is "twenty-one billion, nine hundred thirty-six million, eight hundred sixty-eight thousand, three hundred twenty-one".