21005044 has 6 divisors (see below), whose sum is σ = 36758834. Its totient is φ = 10502520.

The previous prime is 21005041. The next prime is 21005053. The reversal of 21005044 is 44050012.

It can be written as a sum of positive squares in only one way, i.e., 19980900 + 1024144 = 4470^2 + 1012^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005041) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2625627 + ... + 2625634.

Almost surely, 2^21005044 is an apocalyptic number.

It is an amenable number.

21005044 is a deficient number, since it is larger than the sum of its proper divisors (15753790).

21005044 is a wasteful number, since it uses less digits than its factorization.

21005044 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5251265 (or 5251263 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 16.

The square root of 21005044 is about 4583.1260074320. The cubic root of 21005044 is about 275.9145047802.

Adding to 21005044 its reverse (44050012), we get a palindrome (65055056).

The spelling of 21005044 in words is "twenty-one million, five thousand, forty-four".