21800240 has 80 divisors (see below), whose sum is σ = 63210240. Its totient is φ = 6792960.

The previous prime is 21800237. The next prime is 21800281. The reversal of 21800240 is 4200812.

It is a tau number, because it is divible by the number of its divisors (80).

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, 4391 + ... + 7929.

It is an arithmetic number, because the mean of its divisors is an integer number (790128).

Almost surely, 2^21800240 is an apocalyptic number.

21800240 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 21800240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31605120).

21800240 is an abundant number, since it is smaller than the sum of its proper divisors (41410000).

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

21800240 is a wasteful number, since it uses less digits than its factorization.

21800240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3570 (or 3564 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 21800240 is about 4669.0727130770. The cubic root of 21800240 is about 279.3532692669.

The spelling of 21800240 in words is "twenty-one million, eight hundred thousand, two hundred forty".