21311320321 has 4 divisors (see below), whose sum is σ = 21672529200. Its totient is φ = 20950111444.

The previous prime is 21311320297. The next prime is 21311320333. The reversal of 21311320321 is 12302311312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21311320321 - 2¹⁵ = 21311287553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21311320351) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 180604351 + ... + 180604468.

It is an arithmetic number, because the mean of its divisors is an integer number (5418132300).

Almost surely, 2^21311320321 is an apocalyptic number.

It is an amenable number.

21311320321 is a deficient number, since it is larger than the sum of its proper divisors (361208879).

21311320321 is an equidigital number, since it uses as much as digits as its factorization.

21311320321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 361208878.

The product of its (nonzero) digits is 216, while the sum is 19.

Adding to 21311320321 its reverse (12302311312), we get a palindrome (33613631633).

Subtracting from 21311320321 its reverse (12302311312), we obtain a palindrome (9009009009).

The spelling of 21311320321 in words is "twenty-one billion, three hundred eleven million, three hundred twenty thousand, three hundred twenty-one".