21066911 has 4 divisors (see below), whose sum is σ = 21088800. Its totient is φ = 21045024.

The previous prime is 21066863. The next prime is 21066931. The reversal of 21066911 is 11966012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21066911 - 2¹⁰ = 21065887 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21066931) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 9431 + ... + 11448.

It is an arithmetic number, because the mean of its divisors is an integer number (5272200).

Almost surely, 2^21066911 is an apocalyptic number.

21066911 is a deficient number, since it is larger than the sum of its proper divisors (21889).

21066911 is a wasteful number, since it uses less digits than its factorization.

21066911 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21888.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21066911 is about 4589.8704774754. The cubic root of 21066911 is about 276.1851266215.

The spelling of 21066911 in words is "twenty-one million, sixty-six thousand, nine hundred eleven".