21011685 has 16 divisors (see below), whose sum is σ = 33765120. Its totient is φ = 11157440.

The previous prime is 21011659. The next prime is 21011693. The reversal of 21011685 is 58611012.

It is not a de Polignac number, because 21011685 - 2⁶ = 21011621 is a prime.

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, 655 + ... + 6515.

It is an arithmetic number, because the mean of its divisors is an integer number (2110320).

Almost surely, 2^21011685 is an apocalyptic number.

It is an amenable number.

21011685 is a deficient number, since it is larger than the sum of its proper divisors (12753435).

21011685 is a wasteful number, since it uses less digits than its factorization.

21011685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6108.

The product of its (nonzero) digits is 480, while the sum is 24.

The square root of 21011685 is about 4583.8504556759. The cubic root of 21011685 is about 275.9435796246.

Adding to 21011685 its reverse (58611012), we get a palindrome (79622697).

The spelling of 21011685 in words is "twenty-one million, eleven thousand, six hundred eighty-five".