21885865 has 16 divisors (see below), whose sum is σ = 27378000. Its totient is φ = 16774912.

The previous prime is 21885827. The next prime is 21885869. The reversal of 21885865 is 56858812.

It can be written as a sum of positive squares in 8 ways, for example, as 7958041 + 13927824 = 2821^2 + 3732^2 .

It is a cyclic number.

It is not a de Polignac number, because 21885865 - 2⁷ = 21885737 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21885869) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21099 + ... + 22111.

It is an arithmetic number, because the mean of its divisors is an integer number (1711125).

Almost surely, 2^21885865 is an apocalyptic number.

It is an amenable number.

21885865 is a deficient number, since it is larger than the sum of its proper divisors (5492135).

21885865 is a wasteful number, since it uses less digits than its factorization.

21885865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1196.

The product of its digits is 153600, while the sum is 43.

The square root of 21885865 is about 4678.2331066333. The cubic root of 21885865 is about 279.7185309245.

The spelling of 21885865 in words is "twenty-one million, eight hundred eighty-five thousand, eight hundred sixty-five".