21865055 has 4 divisors (see below), whose sum is σ = 26238072. Its totient is φ = 17492040.

The previous prime is 21865037. The next prime is 21865057. The reversal of 21865055 is 55056812.

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-21865055 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 (21865057) 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, 2186501 + ... + 2186510.

It is an arithmetic number, because the mean of its divisors is an integer number (6559518).

Almost surely, 2^21865055 is an apocalyptic number.

21865055 is a deficient number, since it is larger than the sum of its proper divisors (4373017).

21865055 is an equidigital number, since it uses as much as digits as its factorization.

21865055 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4373016.

The product of its (nonzero) digits is 12000, while the sum is 32.

The square root of 21865055 is about 4676.0084473833. The cubic root of 21865055 is about 279.6298467664.

The spelling of 21865055 in words is "twenty-one million, eight hundred sixty-five thousand, fifty-five".