21331331321 has 4 divisors (see below), whose sum is σ = 22066894500. Its totient is φ = 20595768144.

The previous prime is 21331331309. The next prime is 21331331389. The reversal of 21331331321 is 12313313312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 11505565696 + 9825765625 = 107264^2 + 99125^2 .

It is a cyclic number.

It is not a de Polignac number, because 21331331321 - 2³⁰ = 20257589497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21331331221) 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, 367781546 + ... + 367781603.

It is an arithmetic number, because the mean of its divisors is an integer number (5516723625).

Almost surely, 2^21331331321 is an apocalyptic number.

It is an amenable number.

21331331321 is a deficient number, since it is larger than the sum of its proper divisors (735563179).

21331331321 is an equidigital number, since it uses as much as digits as its factorization.

21331331321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 735563178.

The product of its digits is 972, while the sum is 23.

Adding to 21331331321 its reverse (12313313312), we get a palindrome (33644644633).

The spelling of 21331331321 in words is "twenty-one billion, three hundred thirty-one million, three hundred thirty-one thousand, three hundred twenty-one".