21040845 has 24 divisors (see below), whose sum is σ = 39163104. Its totient is φ = 9618336.

The previous prime is 21040807. The next prime is 21040879. The reversal of 21040845 is 54804012.

It is not a de Polignac number, because 21040845 - 2¹² = 21036749 is a prime.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 13579 + ... + 15048.

It is an arithmetic number, because the mean of its divisors is an integer number (1631796).

Almost surely, 2^21040845 is an apocalyptic number.

It is an amenable number.

21040845 is a deficient number, since it is larger than the sum of its proper divisors (18122259).

21040845 is a wasteful number, since it uses less digits than its factorization.

21040845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28649 (or 28642 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 24.

The square root of 21040845 is about 4587.0300849242. The cubic root of 21040845 is about 276.0711720465.

Adding to 21040845 its reverse (54804012), we get a palindrome (75844857).

The spelling of 21040845 in words is "twenty-one million, forty thousand, eight hundred forty-five".