21820885 has 4 divisors (see below), whose sum is σ = 26185068. Its totient is φ = 17456704.

The previous prime is 21820879. The next prime is 21820889. The reversal of 21820885 is 58802812.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17322244 + 4498641 = 4162^2 + 2121^2 .

It is a cyclic number.

It is not a de Polignac number, because 21820885 - 2⁵ = 21820853 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21820885.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820889) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2182084 + ... + 2182093.

It is an arithmetic number, because the mean of its divisors is an integer number (6546267).

Almost surely, 2^21820885 is an apocalyptic number.

It is an amenable number.

21820885 is a deficient number, since it is larger than the sum of its proper divisors (4364183).

21820885 is an equidigital number, since it uses as much as digits as its factorization.

21820885 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4364182.

The product of its (nonzero) digits is 10240, while the sum is 34.

The square root of 21820885 is about 4671.2830143334. The cubic root of 21820885 is about 279.4414246978.

The spelling of 21820885 in words is "twenty-one million, eight hundred twenty thousand, eight hundred eighty-five".