21505044 has 24 divisors (see below), whose sum is σ = 54740448. Its totient is φ = 6516640.

The previous prime is 21505039. The next prime is 21505063. The reversal of 21505044 is 44050512.

It is a self number, because there is not a number n which added to its sum of digits gives 21505044.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 81327 + ... + 81590.

It is an arithmetic number, because the mean of its divisors is an integer number (2280852).

Almost surely, 2^21505044 is an apocalyptic number.

It is an amenable number.

21505044 is an abundant number, since it is smaller than the sum of its proper divisors (33235404).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21505044 is a wasteful number, since it uses less digits than its factorization.

21505044 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162935 (or 162933 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 21505044 is about 4637.3531243588. The cubic root of 21505044 is about 278.0866317312.

Adding to 21505044 its reverse (44050512), we get a palindrome (65555556).

The spelling of 21505044 in words is "twenty-one million, five hundred five thousand, forty-four".