21800000 has 84 divisors (see below), whose sum is σ = 54566820. Its totient is φ = 8640000.

The previous prime is 21799979. The next prime is 21800003. The reversal of 21800000 is 812.

It can be written as a sum of positive squares in 6 ways, for example, as 16192576 + 5607424 = 4024^2 + 2368^2 .

It is not an unprimeable number, because it can be changed into a prime (21800003) 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, 199946 + ... + 200054.

It is an arithmetic number, because the mean of its divisors is an integer number (649605).

Almost surely, 2^21800000 is an apocalyptic number.

21800000 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 21800000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27283410).

21800000 is an abundant number, since it is smaller than the sum of its proper divisors (32766820).

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

21800000 is an frugal number, since it uses more digits than its factorization.

21800000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146 (or 116 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 21800000 is about 4669.0470119715. The cubic root of 21800000 is about 279.3522441248.

Adding to 21800000 its reverse (812), we get a palindrome (21800812).

The spelling of 21800000 in words is "twenty-one million, eight hundred thousand".