21053824 has 64 divisors (see below), whose sum is σ = 48225600. Its totient is φ = 9054720.

The previous prime is 21053783. The next prime is 21053831. The reversal of 21053824 is 42835012.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26359 + ... + 27145.

It is an arithmetic number, because the mean of its divisors is an integer number (753525).

Almost surely, 2^21053824 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21053824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24112800).

21053824 is an abundant number, since it is smaller than the sum of its proper divisors (27171776).

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

21053824 is a wasteful number, since it uses less digits than its factorization.

21053824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 831 (or 819 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 21053824 is about 4588.4446166430. Note that the first 3 decimals coincide. The cubic root of 21053824 is about 276.1279250151.

Adding to 21053824 its reverse (42835012), we get a palindrome (63888836).

It can be divided in two parts, 2105 and 3824, that added together give a square (5929 = 77²).

The spelling of 21053824 in words is "twenty-one million, fifty-three thousand, eight hundred twenty-four".