21085057 has 8 divisors (see below), whose sum is σ = 24223616. Its totient is φ = 17978112.

The previous prime is 21085039. The next prime is 21085061. The reversal of 21085057 is 75058012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21085057 - 2²³ = 12696449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21085037) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6453 + ... + 9154.

It is an arithmetic number, because the mean of its divisors is an integer number (3027952).

Almost surely, 2^21085057 is an apocalyptic number.

It is an amenable number.

21085057 is a deficient number, since it is larger than the sum of its proper divisors (3138559).

21085057 is a wasteful number, since it uses less digits than its factorization.

21085057 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15807.

The product of its (nonzero) digits is 2800, while the sum is 28.

The square root of 21085057 is about 4591.8467962248. The cubic root of 21085057 is about 276.2644012885.

The spelling of 21085057 in words is "twenty-one million, eighty-five thousand, fifty-seven".