21808224 has 96 divisors (see below), whose sum is σ = 65197440. Its totient is φ = 7088256.

The previous prime is 21808217. The next prime is 21808231. The reversal of 21808224 is 42280812.

It is an interprime number because it is at equal distance from previous prime (21808217) and next prime (21808231).

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36859 + ... + 37445.

It is an arithmetic number, because the mean of its divisors is an integer number (679140).

Almost surely, 2^21808224 is an apocalyptic number.

21808224 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 21808224, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32598720).

21808224 is an abundant number, since it is smaller than the sum of its proper divisors (43389216).

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

21808224 is a wasteful number, since it uses less digits than its factorization.

21808224 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 649 (or 635 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 27.

The square root of 21808224 is about 4669.9276225655. The cubic root of 21808224 is about 279.3873680395.

It can be divided in two parts, 2180 and 8224, that added together give a square (10404 = 102²).

The spelling of 21808224 in words is "twenty-one million, eight hundred eight thousand, two hundred twenty-four".