21213442321 has 4 divisors (see below), whose sum is σ = 21897746944. Its totient is φ = 20529137700.

The previous prime is 21213442307. The next prime is 21213442331. The reversal of 21213442321 is 12324431212.

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 a de Polignac number, because none of the positive numbers 2^k-21213442321 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21213442331) 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, 342152265 + ... + 342152326.

It is an arithmetic number, because the mean of its divisors is an integer number (5474436736).

Almost surely, 2^21213442321 is an apocalyptic number.

It is an amenable number.

21213442321 is a deficient number, since it is larger than the sum of its proper divisors (684304623).

21213442321 is an equidigital number, since it uses as much as digits as its factorization.

21213442321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 684304622.

The product of its digits is 2304, while the sum is 25.

Adding to 21213442321 its reverse (12324431212), we get a palindrome (33537873533).

The spelling of 21213442321 in words is "twenty-one billion, two hundred thirteen million, four hundred forty-two thousand, three hundred twenty-one".