21678812 has 6 divisors (see below), whose sum is σ = 37937928. Its totient is φ = 10839404.

The previous prime is 21678809. The next prime is 21678823. The reversal of 21678812 is 21887612.

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 as a sum of consecutive naturals, namely, 2709848 + ... + 2709855.

It is an arithmetic number, because the mean of its divisors is an integer number (6322988).

Almost surely, 2^21678812 is an apocalyptic number.

It is an amenable number.

21678812 is a deficient number, since it is larger than the sum of its proper divisors (16259116).

21678812 is a wasteful number, since it uses less digits than its factorization.

21678812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5419707 (or 5419705 counting only the distinct ones).

The product of its digits is 10752, while the sum is 35.

The square root of 21678812 is about 4656.0511165579. The cubic root of 21678812 is about 278.8336345395.

The spelling of 21678812 in words is "twenty-one million, six hundred seventy-eight thousand, eight hundred twelve".