21921024 has 144 divisors (see below), whose sum is σ = 65342592. Its totient is φ = 6488064.

The previous prime is 21921017. The next prime is 21921059. The reversal of 21921024 is 42012912.

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 15 ways as a sum of consecutive naturals, for example, 300252 + ... + 300324.

It is an arithmetic number, because the mean of its divisors is an integer number (453768).

Almost surely, 2^21921024 is an apocalyptic number.

21921024 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21921024, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32671296).

21921024 is an abundant number, since it is smaller than the sum of its proper divisors (43421568).

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

21921024 is a wasteful number, since it uses less digits than its factorization.

21921024 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132 (or 118 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 21921024 is about 4681.9893207909. The cubic root of 21921024 is about 279.8682373244.

Adding to 21921024 its reverse (42012912), we get a palindrome (63933936).

The spelling of 21921024 in words is "twenty-one million, nine hundred twenty-one thousand, twenty-four".