21678866 has 8 divisors (see below), whose sum is σ = 35474544. Its totient is φ = 9854020.

The previous prime is 21678823. The next prime is 21678907. The reversal of 21678866 is 66887612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon 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 3 ways as a sum of consecutive naturals, for example, 492680 + ... + 492723.

It is an arithmetic number, because the mean of its divisors is an integer number (4434318).

Almost surely, 2^21678866 is an apocalyptic number.

21678866 is a deficient number, since it is larger than the sum of its proper divisors (13795678).

21678866 is a wasteful number, since it uses less digits than its factorization.

21678866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 985416.

The product of its digits is 193536, while the sum is 44.

The square root of 21678866 is about 4656.0569154597. The cubic root of 21678866 is about 278.8338660559.

The spelling of 21678866 in words is "twenty-one million, six hundred seventy-eight thousand, eight hundred sixty-six".