21805600 has 72 divisors (see below), whose sum is σ = 53973108. Its totient is φ = 8601600.

The previous prime is 21805579. The next prime is 21805607. The reversal of 21805600 is 650812.

It is a happy number.

It can be written as a sum of positive squares in 6 ways, for example, as 9217296 + 12588304 = 3036^2 + 3548^2 .

It is not an unprimeable number, because it can be changed into a prime (21805607) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 77460 + ... + 77740.

Almost surely, 2^21805600 is an apocalyptic number.

21805600 is a gapful number since it is divisible by the number (20) 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 21805600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26986554).

21805600 is an abundant number, since it is smaller than the sum of its proper divisors (32167508).

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

21805600 is a wasteful number, since it uses less digits than its factorization.

21805600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 398 (or 385 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21805600 is about 4669.6466675756. The cubic root of 21805600 is about 279.3761621467.

The spelling of 21805600 in words is "twenty-one million, eight hundred five thousand, six hundred".