21388866 has 16 divisors (see below), whose sum is σ = 43157664. Its totient is φ = 7066304.

The previous prime is 21388837. The next prime is 21388867. The reversal of 21388866 is 66888312.

It is not an unprimeable number, because it can be changed into a prime (21388867) by changing a digit.

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, 15096 + ... + 16451.

It is an arithmetic number, because the mean of its divisors is an integer number (2697354).

Almost surely, 2^21388866 is an apocalyptic number.

21388866 is an abundant number, since it is smaller than the sum of its proper divisors (21768798).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21388866 is a wasteful number, since it uses less digits than its factorization.

21388866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31665.

The product of its digits is 110592, while the sum is 42.

The square root of 21388866 is about 4624.8098339283. The cubic root of 21388866 is about 277.5849524824.

The spelling of 21388866 in words is "twenty-one million, three hundred eighty-eight thousand, eight hundred sixty-six".