21091844 has 24 divisors (see below), whose sum is σ = 38068800. Its totient is φ = 10219104.

The previous prime is 21091841. The next prime is 21091867. The reversal of 21091844 is 44819012.

It is not an unprimeable number, because it can be changed into a prime (21091841) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25217 + ... + 26039.

It is an arithmetic number, because the mean of its divisors is an integer number (1586200).

Almost surely, 2^21091844 is an apocalyptic number.

It is an amenable number.

21091844 is a deficient number, since it is larger than the sum of its proper divisors (16976956).

21091844 is a wasteful number, since it uses less digits than its factorization.

21091844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1019 (or 1017 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21091844 is about 4592.5857640332. The cubic root of 21091844 is about 276.2940400566.

The spelling of 21091844 in words is "twenty-one million, ninety-one thousand, eight hundred forty-four".