21805738 has 16 divisors (see below), whose sum is σ = 34272000. Its totient is φ = 10391472.

The previous prime is 21805699. The next prime is 21805739. The reversal of 21805738 is 83750812.

It is not an unprimeable number, because it can be changed into a prime (21805739) 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 7 ways as a sum of consecutive naturals, for example, 2203 + ... + 6961.

It is an arithmetic number, because the mean of its divisors is an integer number (2142000).

Almost surely, 2^21805738 is an apocalyptic number.

21805738 is a deficient number, since it is larger than the sum of its proper divisors (12466262).

21805738 is a wasteful number, since it uses less digits than its factorization.

21805738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4869.

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 21805738 is about 4669.6614438308. The cubic root of 21805738 is about 279.3767515034.

The spelling of 21805738 in words is "twenty-one million, eight hundred five thousand, seven hundred thirty-eight".