21321455621 has 16 divisors (see below), whose sum is σ = 22279907328. Its totient is φ = 20380896000.

The previous prime is 21321455591. The next prime is 21321455633. The reversal of 21321455621 is 12655412312.

It is a cyclic number.

It is not a de Polignac number, because 21321455621 - 2³⁴ = 4141586437 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321455521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1347860 + ... + 1363586.

It is an arithmetic number, because the mean of its divisors is an integer number (1392494208).

Almost surely, 2^21321455621 is an apocalyptic number.

It is an amenable number.

21321455621 is a deficient number, since it is larger than the sum of its proper divisors (958451707).

21321455621 is a wasteful number, since it uses less digits than its factorization.

21321455621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16292.

The product of its digits is 14400, while the sum is 32.

Adding to 21321455621 its reverse (12655412312), we get a palindrome (33976867933).

The spelling of 21321455621 in words is "twenty-one billion, three hundred twenty-one million, four hundred fifty-five thousand, six hundred twenty-one".