21707865 has 32 divisors (see below), whose sum is σ = 38960640. Its totient is φ = 11467008.

The previous prime is 21707849. The next prime is 21707893. The reversal of 21707865 is 56870712.

It is not a de Polignac number, because 21707865 - 2⁴ = 21707849 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 14544 + ... + 15966.

It is an arithmetic number, because the mean of its divisors is an integer number (1217520).

Almost surely, 2^21707865 is an apocalyptic number.

It is an amenable number.

21707865 is a deficient number, since it is larger than the sum of its proper divisors (17252775).

21707865 is a wasteful number, since it uses less digits than its factorization.

21707865 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1550 (or 1544 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The square root of 21707865 is about 4659.1699904597. The cubic root of 21707865 is about 278.9581391699.

The spelling of 21707865 in words is "twenty-one million, seven hundred seven thousand, eight hundred sixty-five".