21553105021 has 4 divisors (see below), whose sum is σ = 24632120032. Its totient is φ = 18474090012.

The previous prime is 21553104977. The next prime is 21553105039. The reversal of 21553105021 is 12050135512.

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 not a de Polignac number, because 21553105021 - 2⁷ = 21553104893 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 (21553405021) 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, 1539507495 + ... + 1539507508.

It is an arithmetic number, because the mean of its divisors is an integer number (6158030008).

Almost surely, 2^21553105021 is an apocalyptic number.

It is an amenable number.

21553105021 is a deficient number, since it is larger than the sum of its proper divisors (3079015011).

21553105021 is an equidigital number, since it uses as much as digits as its factorization.

21553105021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3079015010.

The product of its (nonzero) digits is 1500, while the sum is 25.

The spelling of 21553105021 in words is "twenty-one billion, five hundred fifty-three million, one hundred five thousand, twenty-one".