21573866 has 16 divisors (see below), whose sum is σ = 33121440. Its totient is φ = 10536240.

The previous prime is 21573863. The next prime is 21573887. The reversal of 21573866 is 66837512.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21573863) 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, 16940 + ... + 18168.

It is an arithmetic number, because the mean of its divisors is an integer number (2070090).

Almost surely, 2^21573866 is an apocalyptic number.

21573866 is a deficient number, since it is larger than the sum of its proper divisors (11547574).

21573866 is a wasteful number, since it uses less digits than its factorization.

21573866 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1429.

The product of its digits is 60480, while the sum is 38.

The square root of 21573866 is about 4644.7675937554. The cubic root of 21573866 is about 278.3829668340.

The spelling of 21573866 in words is "twenty-one million, five hundred seventy-three thousand, eight hundred sixty-six".