21105545155 has 4 divisors (see below), whose sum is σ = 25326654192. Its totient is φ = 16884436120.

The previous prime is 21105545137. The next prime is 21105545171. The reversal of 21105545155 is 55154550112.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21105545155 - 2¹⁵ = 21105512387 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21105545155.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2110554511 + ... + 2110554520.

It is an arithmetic number, because the mean of its divisors is an integer number (6331663548).

Almost surely, 2^21105545155 is an apocalyptic number.

21105545155 is a deficient number, since it is larger than the sum of its proper divisors (4221109037).

21105545155 is an equidigital number, since it uses as much as digits as its factorization.

21105545155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4221109036.

The product of its (nonzero) digits is 25000, while the sum is 34.

The spelling of 21105545155 in words is "twenty-one billion, one hundred five million, five hundred forty-five thousand, one hundred fifty-five".