21140865 has 32 divisors (see below), whose sum is σ = 37872000. Its totient is φ = 11188800.

The previous prime is 21140857. The next prime is 21140869. The reversal of 21140865 is 56804112.

It is not a de Polignac number, because 21140865 - 2³ = 21140857 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21140869) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19590 + ... + 20640.

It is an arithmetic number, because the mean of its divisors is an integer number (1183500).

Almost surely, 2^21140865 is an apocalyptic number.

It is an amenable number.

21140865 is a deficient number, since it is larger than the sum of its proper divisors (16731135).

21140865 is a wasteful number, since it uses less digits than its factorization.

21140865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1214 (or 1208 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21140865 is about 4597.9196382712. The cubic root of 21140865 is about 276.5079257440.

Adding to 21140865 its reverse (56804112), we get a palindrome (77944977).

The spelling of 21140865 in words is "twenty-one million, one hundred forty thousand, eight hundred sixty-five".