21023042555 has 4 divisors (see below), whose sum is σ = 25227651072. Its totient is φ = 16818434040.

The previous prime is 21023042477. The next prime is 21023042597. The reversal of 21023042555 is 55524032012.

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

It is not a de Polignac number, because 21023042555 - 2¹⁸ = 21022780411 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2102304251 + ... + 2102304260.

It is an arithmetic number, because the mean of its divisors is an integer number (6306912768).

Almost surely, 2^21023042555 is an apocalyptic number.

21023042555 is a deficient number, since it is larger than the sum of its proper divisors (4204608517).

21023042555 is an equidigital number, since it uses as much as digits as its factorization.

21023042555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4204608516.

The product of its (nonzero) digits is 12000, while the sum is 29.

Adding to 21023042555 its reverse (55524032012), we get a palindrome (76547074567).

The spelling of 21023042555 in words is "twenty-one billion, twenty-three million, forty-two thousand, five hundred fifty-five".