21684685 has 32 divisors (see below), whose sum is σ = 29766528. Its totient is φ = 15025920.

The previous prime is 21684679. The next prime is 21684713. The reversal of 21684685 is 58648612.

It is not a de Polignac number, because 21684685 - 2⁷ = 21684557 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 31 ways as a sum of consecutive naturals, for example, 125259 + ... + 125431.

It is an arithmetic number, because the mean of its divisors is an integer number (930204).

Almost surely, 2^21684685 is an apocalyptic number.

It is an amenable number.

21684685 is a deficient number, since it is larger than the sum of its proper divisors (8081843).

21684685 is a wasteful number, since it uses less digits than its factorization.

21684685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 285.

The product of its digits is 92160, while the sum is 40.

The square root of 21684685 is about 4656.6817585057. The cubic root of 21684685 is about 278.8588118428.

The spelling of 21684685 in words is "twenty-one million, six hundred eighty-four thousand, six hundred eighty-five".