21805700 has 36 divisors (see below), whose sum is σ = 54079872. Its totient is φ = 7476000.

The previous prime is 21805699. The next prime is 21805739. The reversal of 21805700 is 750812.

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 11 ways as a sum of consecutive naturals, for example, 14876 + ... + 16275.

Almost surely, 2^21805700 is an apocalyptic number.

21805700 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21805700 is an abundant number, since it is smaller than the sum of its proper divisors (32274172).

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

21805700 is a wasteful number, since it uses less digits than its factorization.

21805700 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31172 (or 31165 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 23.

The square root of 21805700 is about 4669.6573750116. The cubic root of 21805700 is about 279.3765892170.

The spelling of 21805700 in words is "twenty-one million, eight hundred five thousand, seven hundred".