21123055 has 4 divisors (see below), whose sum is σ = 25347672. Its totient is φ = 16898440.

The previous prime is 21123043. The next prime is 21123073. The reversal of 21123055 is 55032112.

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

It is a de Polignac number, because none of the positive numbers 2^k-21123055 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 2112301 + ... + 2112310.

It is an arithmetic number, because the mean of its divisors is an integer number (6336918).

Almost surely, 2^21123055 is an apocalyptic number.

21123055 is a deficient number, since it is larger than the sum of its proper divisors (4224617).

21123055 is an equidigital number, since it uses as much as digits as its factorization.

21123055 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4224616.

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21123055 is about 4595.9824847360. The cubic root of 21123055 is about 276.4302564259.

Adding to 21123055 its reverse (55032112), we get a palindrome (76155167).

The spelling of 21123055 in words is "twenty-one million, one hundred twenty-three thousand, fifty-five".