21311800 has 96 divisors (see below), whose sum is σ = 53434080. Its totient is φ = 7884800.

The previous prime is 21311767. The next prime is 21311809. The reversal of 21311800 is 811312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311809) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 188544 + ... + 188656.

It is an arithmetic number, because the mean of its divisors is an integer number (556605).

Almost surely, 2^21311800 is an apocalyptic number.

21311800 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 21311800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26717040).

21311800 is an abundant number, since it is smaller than the sum of its proper divisors (32122280).

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

21311800 is a wasteful number, since it uses less digits than its factorization.

21311800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193 (or 184 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 16.

The square root of 21311800 is about 4616.4705132818. The cubic root of 21311800 is about 277.2511634546.

The spelling of 21311800 in words is "twenty-one million, three hundred eleven thousand, eight hundred".