21399886369 has 9 divisors (see below), whose sum is σ = 21524511411. Its totient is φ = 21275981280.

The previous prime is 21399886367. The next prime is 21399886441. The reversal of 21399886369 is 96368899312.

The square root of 21399886369 is 146287.

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., 16094220769 + 5305665600 = 126863^2 + 72840^2 .

It is not a de Polignac number, because 21399886369 - 2¹ = 21399886367 is a prime.

It is a super-2 number, since 2×21399886369² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21399886369.

It is not an unprimeable number, because it can be changed into a prime (21399886367) 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, 35254864 + ... + 35255470.

It is an arithmetic number, because the mean of its divisors is an integer number (2391612379).

Almost surely, 2^21399886369 is an apocalyptic number.

21399886369 is the 146287-th square number.

21399886369 is the 73144-th centered octagonal number.

It is an amenable number.

21399886369 is a deficient number, since it is larger than the sum of its proper divisors (124625042).

21399886369 is an frugal number, since it uses more digits than its factorization.

21399886369 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1696 (or 848 counting only the distinct ones).

The product of its digits is 30233088, while the sum is 64.

Multiplying 21399886369 by its sum of digits (64), we get a square (1369592727616 = 1170296²).

The spelling of 21399886369 in words is "twenty-one billion, three hundred ninety-nine million, eight hundred eighty-six thousand, three hundred sixty-nine".