21213166321 has 4 divisors (see below), whose sum is σ = 22460999652. Its totient is φ = 19965332992.

The previous prime is 21213166309. The next prime is 21213166333. The reversal of 21213166321 is 12366131212.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21213166309) and next prime (21213166333).

It can be written as a sum of positive squares in 2 ways, for example, as 13908900096 + 7304266225 = 117936^2 + 85465^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213166321 - 2³³ = 12623231729 is a prime.

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 21213166321.

It is not an unprimeable number, because it can be changed into a prime (21213166021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 623916640 + ... + 623916673.

It is an arithmetic number, because the mean of its divisors is an integer number (5615249913).

Almost surely, 2^21213166321 is an apocalyptic number.

It is an amenable number.

21213166321 is a deficient number, since it is larger than the sum of its proper divisors (1247833331).

21213166321 is a wasteful number, since it uses less digits than its factorization.

21213166321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1247833330.

The product of its digits is 2592, while the sum is 28.

Adding to 21213166321 its reverse (12366131212), we get a palindrome (33579297533).

The spelling of 21213166321 in words is "twenty-one billion, two hundred thirteen million, one hundred sixty-six thousand, three hundred twenty-one".