21684590 has 32 divisors (see below), whose sum is σ = 40547520. Its totient is φ = 8342784.

The previous prime is 21684589. The next prime is 21684623. The reversal of 21684590 is 9548612.

It is a self number, because there is not a number n which added to its sum of digits gives 21684590.

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, 37826 + ... + 38394.

It is an arithmetic number, because the mean of its divisors is an integer number (1267110).

Almost surely, 2^21684590 is an apocalyptic number.

21684590 is a deficient number, since it is larger than the sum of its proper divisors (18862930).

21684590 is a wasteful number, since it uses less digits than its factorization.

21684590 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 716.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 21684590 is about 4656.6715580981. The cubic root of 21684590 is about 278.8584046180.

The spelling of 21684590 in words is "twenty-one million, six hundred eighty-four thousand, five hundred ninety".