21085055 has 4 divisors (see below), whose sum is σ = 25302072. Its totient is φ = 16868040.

The previous prime is 21085039. The next prime is 21085061. The reversal of 21085055 is 55058012.

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

It is not a de Polignac number, because 21085055 - 2⁴ = 21085039 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, 2108501 + ... + 2108510.

It is an arithmetic number, because the mean of its divisors is an integer number (6325518).

Almost surely, 2^21085055 is an apocalyptic number.

21085055 is a deficient number, since it is larger than the sum of its proper divisors (4217017).

21085055 is an equidigital number, since it uses as much as digits as its factorization.

21085055 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4217016.

The product of its (nonzero) digits is 2000, while the sum is 26.

The square root of 21085055 is about 4591.8465784475. The cubic root of 21085055 is about 276.2643925536.

The spelling of 21085055 in words is "twenty-one million, eighty-five thousand, fifty-five".