21185900 has 18 divisors (see below), whose sum is σ = 45973620. Its totient is φ = 8474320.

The previous prime is 21185891. The next prime is 21185917. The reversal of 21185900 is 958112.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21185900.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 105830 + ... + 106029.

It is an arithmetic number, because the mean of its divisors is an integer number (2554090).

Almost surely, 2^21185900 is an apocalyptic number.

21185900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21185900 is an abundant number, since it is smaller than the sum of its proper divisors (24787720).

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

21185900 is a wasteful number, since it uses less digits than its factorization.

21185900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211873 (or 211866 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 21185900 is about 4602.8143564563. The cubic root of 21185900 is about 276.7041287315.

The spelling of 21185900 in words is "twenty-one million, one hundred eighty-five thousand, nine hundred".