21305321215021 has 4 divisors (see below), whose sum is σ = 21992589641344. Its totient is φ = 20618052788700.

The previous prime is 21305321215019. The next prime is 21305321215103. The reversal of 21305321215021 is 12051212350312.

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 21305321215021 - 2¹ = 21305321215019 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305321215121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 343634213115 + ... + 343634213176.

It is an arithmetic number, because the mean of its divisors is an integer number (5498147410336).

Almost surely, 2^{21305321215021} is an apocalyptic number.

It is an amenable number.

21305321215021 is a deficient number, since it is larger than the sum of its proper divisors (687268426323).

21305321215021 is an equidigital number, since it uses as much as digits as its factorization.

21305321215021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 687268426322.

The product of its (nonzero) digits is 3600, while the sum is 28.

Adding to 21305321215021 its reverse (12051212350312), we get a palindrome (33356533565333).

The spelling of 21305321215021 in words is "twenty-one trillion, three hundred five billion, three hundred twenty-one million, two hundred fifteen thousand, twenty-one".