21331213021 has 2 divisors, whose sum is σ = 21331213022. Its totient is φ = 21331213020.

The previous prime is 21331213019. The next prime is 21331213031. The reversal of 21331213021 is 12031213312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13389729796 + 7941483225 = 115714^2 + 89115^2 .

It is a cyclic number.

It is not a de Polignac number, because 21331213021 - 2¹ = 21331213019 is a prime.

Together with 21331213019, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21331213021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21331213031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10665606510 + 10665606511.

It is an arithmetic number, because the mean of its divisors is an integer number (10665606511).

Almost surely, 2^21331213021 is an apocalyptic number.

It is an amenable number.

21331213021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331213021 is an equidigital number, since it uses as much as digits as its factorization.

21331213021 is an evil number, because the sum of its binary digits is even.

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

Adding to 21331213021 its reverse (12031213312), we get a palindrome (33362426333).

The spelling of 21331213021 in words is "twenty-one billion, three hundred thirty-one million, two hundred thirteen thousand, twenty-one".