21205085 has 16 divisors (see below), whose sum is σ = 28657152. Its totient is φ = 14923200.

The previous prime is 21205049. The next prime is 21205099. The reversal of 21205085 is 58050212.

It is not a de Polignac number, because 21205085 - 2⁶ = 21205021 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21205085.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 4514 + ... + 7923.

It is an arithmetic number, because the mean of its divisors is an integer number (1791072).

Almost surely, 2^21205085 is an apocalyptic number.

It is an amenable number.

21205085 is a deficient number, since it is larger than the sum of its proper divisors (7452067).

21205085 is a wasteful number, since it uses less digits than its factorization.

21205085 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12484.

The product of its (nonzero) digits is 800, while the sum is 23.

The square root of 21205085 is about 4604.8979358939. The cubic root of 21205085 is about 276.7876271450.

Adding to 21205085 its reverse (58050212), we get a palindrome (79255297).

The spelling of 21205085 in words is "twenty-one million, two hundred five thousand, eighty-five".