21044813 has 2 divisors, whose sum is σ = 21044814. Its totient is φ = 21044812.

The previous prime is 21044797. The next prime is 21044831. The reversal of 21044813 is 31844012.

Together with next prime (21044831) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15389929 + 5654884 = 3923^2 + 2378^2 .

It is a cyclic number.

It is not a de Polignac number, because 21044813 - 2⁴ = 21044797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21044833) 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 as a sum of consecutive naturals, namely, 10522406 + 10522407.

It is an arithmetic number, because the mean of its divisors is an integer number (10522407).

Almost surely, 2^21044813 is an apocalyptic number.

It is an amenable number.

21044813 is a deficient number, since it is larger than the sum of its proper divisors (1).

21044813 is an equidigital number, since it uses as much as digits as its factorization.

21044813 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 21044813 is about 4587.4625884033. The cubic root of 21044813 is about 276.0885253032.

Adding to 21044813 its reverse (31844012), we get a palindrome (52888825).

The spelling of 21044813 in words is "twenty-one million, forty-four thousand, eight hundred thirteen".