21684704 has 12 divisors (see below), whose sum is σ = 42691824. Its totient is φ = 10842336.

The previous prime is 21684679. The next prime is 21684713. The reversal of 21684704 is 40748612.

It is a Harshad number since it is a multiple of its sum of digits (32), and also a Moran number because the ratio is a prime number: 677647 = 21684704 / (2 + 1 + 6 + 8 + 4 + 7 + 0 + 4).

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 as a sum of consecutive naturals, namely, 338792 + ... + 338855.

It is an arithmetic number, because the mean of its divisors is an integer number (3557652).

Almost surely, 2^21684704 is an apocalyptic number.

It is an amenable number.

21684704 is a deficient number, since it is larger than the sum of its proper divisors (21007120).

21684704 is an equidigital number, since it uses as much as digits as its factorization.

21684704 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 677657 (or 677649 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 32.

The square root of 21684704 is about 4656.6837985846. The cubic root of 21684704 is about 278.8588932877.

The spelling of 21684704 in words is "twenty-one million, six hundred eighty-four thousand, seven hundred four".