21221800 has 24 divisors (see below), whose sum is σ = 49341150. Its totient is φ = 8488640.

The previous prime is 21221791. The next prime is 21221821. The reversal of 21221800 is 812212.

It can be written as a sum of positive squares in 3 ways, for example, as 20304036 + 917764 = 4506^2 + 958^2 .

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, 52855 + ... + 53254.

Almost surely, 2^21221800 is an apocalyptic number.

21221800 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21221800 is an abundant number, since it is smaller than the sum of its proper divisors (28119350).

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

21221800 is a wasteful number, since it uses less digits than its factorization.

21221800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106125 (or 106116 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 21221800 is about 4606.7124937421. The cubic root of 21221800 is about 276.8603343926.

The spelling of 21221800 in words is "twenty-one million, two hundred twenty-one thousand, eight hundred".