21170685 has 16 divisors (see below), whose sum is σ = 34038720. Its totient is φ = 11235840.

The previous prime is 21170671. The next prime is 21170717. The reversal of 21170685 is 58607112.

It is not a de Polignac number, because 21170685 - 2¹⁵ = 21137917 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 (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 180 + ... + 6509.

It is an arithmetic number, because the mean of its divisors is an integer number (2127420).

Almost surely, 2^21170685 is an apocalyptic number.

It is an amenable number.

21170685 is a deficient number, since it is larger than the sum of its proper divisors (12868035).

21170685 is a wasteful number, since it uses less digits than its factorization.

21170685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6908.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 21170685 is about 4601.1612664631. The cubic root of 21170685 is about 276.6378730054.

Adding to 21170685 its reverse (58607112), we get a palindrome (79777797).

The spelling of 21170685 in words is "twenty-one million, one hundred seventy thousand, six hundred eighty-five".