21107865 has 16 divisors (see below), whose sum is σ = 33991488. Its totient is φ = 11184576.

The previous prime is 21107861. The next prime is 21107909. The reversal of 21107865 is 56870112.

It is not a de Polignac number, because 21107865 - 2² = 21107861 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21107861) 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, 2127 + ... + 6836.

It is an arithmetic number, because the mean of its divisors is an integer number (2124468).

Almost surely, 2^21107865 is an apocalyptic number.

It is an amenable number.

21107865 is a deficient number, since it is larger than the sum of its proper divisors (12883623).

21107865 is a wasteful number, since it uses less digits than its factorization.

21107865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9128.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 21107865 is about 4594.3296573058. The cubic root of 21107865 is about 276.3639784101.

Adding to 21107865 its reverse (56870112), we get a palindrome (77977977).

The spelling of 21107865 in words is "twenty-one million, one hundred seven thousand, eight hundred sixty-five".