21800090 has 48 divisors (see below), whose sum is σ = 44315208. Its totient is φ = 7675008.

The previous prime is 21800089. The next prime is 21800101. The reversal of 21800090 is 9000812.

It can be written as a sum of positive squares in 4 ways, for example, as 7745089 + 14055001 = 2783^2 + 3749^2 .

It is a Curzon number.

It is a congruent number.

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 23 ways as a sum of consecutive naturals, for example, 68612 + ... + 68928.

Almost surely, 2^21800090 is an apocalyptic number.

21800090 is an abundant number, since it is smaller than the sum of its proper divisors (22515118).

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

21800090 is a wasteful number, since it uses less digits than its factorization.

21800090 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 383 (or 360 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 21800090 is about 4669.0566499026. The cubic root of 21800090 is about 279.3526285539.

The spelling of 21800090 in words is "twenty-one million, eight hundred thousand, ninety".