21055242021 has 16 divisors (see below), whose sum is σ = 30629007360. Its totient is φ = 12759419120.

The previous prime is 21055242011. The next prime is 21055242037. The reversal of 21055242021 is 12024255012.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21055242021 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21055241982 and 21055242000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21055242011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 354556 + ... + 409658.

It is an arithmetic number, because the mean of its divisors is an integer number (1914312960).

Almost surely, 2^21055242021 is an apocalyptic number.

It is an amenable number.

21055242021 is a deficient number, since it is larger than the sum of its proper divisors (9573765339).

21055242021 is a wasteful number, since it uses less digits than its factorization.

21055242021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66696.

The product of its (nonzero) digits is 1600, while the sum is 24.

Adding to 21055242021 its reverse (12024255012), we get a palindrome (33079497033).

The spelling of 21055242021 in words is "twenty-one billion, fifty-five million, two hundred forty-two thousand, twenty-one".