21643824 has 20 divisors (see below), whose sum is σ = 55913336. Its totient is φ = 7214592.

The previous prime is 21643823. The next prime is 21643841. The reversal of 21643824 is 42834612.

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 21643791 and 21643800.

It is not an unprimeable number, because it can be changed into a prime (21643823) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 225409 + ... + 225504.

Almost surely, 2^21643824 is an apocalyptic number.

21643824 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21643824 is an abundant number, since it is smaller than the sum of its proper divisors (34269512).

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

21643824 is a wasteful number, since it uses less digits than its factorization.

21643824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 450924 (or 450918 counting only the distinct ones).

The product of its digits is 9216, while the sum is 30.

The square root of 21643824 is about 4652.2923381920. The cubic root of 21643824 is about 278.6835481431.

The spelling of 21643824 in words is "twenty-one million, six hundred forty-three thousand, eight hundred twenty-four".