21789824 has 64 divisors (see below), whose sum is σ = 50379840. Its totient is φ = 9194496.

The previous prime is 21789797. The next prime is 21789839. The reversal of 21789824 is 42898712.

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

It is a super-3 number, since 3×21789824³ (a number of 23 digits) contains 333 as substring.

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, 74222 + ... + 74514.

It is an arithmetic number, because the mean of its divisors is an integer number (787185).

Almost surely, 2^21789824 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 21789824, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25189920).

21789824 is an abundant number, since it is smaller than the sum of its proper divisors (28590016).

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

21789824 is an equidigital number, since it uses as much as digits as its factorization.

21789824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 397 (or 385 counting only the distinct ones).

The product of its digits is 64512, while the sum is 41.

The square root of 21789824 is about 4667.9571549019. The cubic root of 21789824 is about 279.3087711758.

The spelling of 21789824 in words is "twenty-one million, seven hundred eighty-nine thousand, eight hundred twenty-four".