21045865 has 8 divisors (see below), whose sum is σ = 25300800. Its totient is φ = 16806192.

The previous prime is 21045853. The next prime is 21045883. The reversal of 21045865 is 56854012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21045865 - 2⁷ = 21045737 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 519 + ... + 6508.

It is an arithmetic number, because the mean of its divisors is an integer number (3162600).

Almost surely, 2^21045865 is an apocalyptic number.

It is an amenable number.

21045865 is a deficient number, since it is larger than the sum of its proper divisors (4254935).

21045865 is an equidigital number, since it uses as much as digits as its factorization.

21045865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7631.

The product of its (nonzero) digits is 9600, while the sum is 31.

The square root of 21045865 is about 4587.5772473060. The cubic root of 21045865 is about 276.0931256496.

Adding to 21045865 its reverse (56854012), we get a palindrome (77899877).

The spelling of 21045865 in words is "twenty-one million, forty-five thousand, eight hundred sixty-five".