21684806 has 16 divisors (see below), whose sum is σ = 38214288. Its totient is φ = 9098400.

The previous prime is 21684799. The next prime is 21684811. The reversal of 21684806 is 60848612.

It is a super-3 number, since 3×21684806³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

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 7 ways as a sum of consecutive naturals, for example, 37625 + ... + 38196.

It is an arithmetic number, because the mean of its divisors is an integer number (2388393).

Almost surely, 2^21684806 is an apocalyptic number.

21684806 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21684806 is a deficient number, since it is larger than the sum of its proper divisors (16529482).

21684806 is a wasteful number, since it uses less digits than its factorization.

21684806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75847.

The product of its (nonzero) digits is 18432, while the sum is 35.

The square root of 21684806 is about 4656.6947505715. The cubic root of 21684806 is about 278.8593305169.

The spelling of 21684806 in words is "twenty-one million, six hundred eighty-four thousand, eight hundred six".