21109824 has 84 divisors (see below), whose sum is σ = 61522864. Its totient is φ = 6918912.

The previous prime is 21109799. The next prime is 21109841. The reversal of 21109824 is 42890112.

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 11 ways as a sum of consecutive naturals, for example, 38319 + ... + 38865.

Almost surely, 2^21109824 is an apocalyptic number.

21109824 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 21109824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30761432).

21109824 is an abundant number, since it is smaller than the sum of its proper divisors (40413040).

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

21109824 is a wasteful number, since it uses less digits than its factorization.

21109824 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 632 (or 619 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 21109824 is about 4594.5428499471. The cubic root of 21109824 is about 276.3725278345.

Adding to 21109824 its reverse (42890112), we get a palindrome (63999936).

The spelling of 21109824 in words is "twenty-one million, one hundred nine thousand, eight hundred twenty-four".