21706865 has 4 divisors (see below), whose sum is σ = 26048244. Its totient is φ = 17365488.

The previous prime is 21706837. The next prime is 21706889. The reversal of 21706865 is 56860712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9935104 + 11771761 = 3152^2 + 3431^2 .

It is a cyclic number.

It is not a de Polignac number, because 21706865 - 2⁸ = 21706609 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2170682 + ... + 2170691.

It is an arithmetic number, because the mean of its divisors is an integer number (6512061).

Almost surely, 2^21706865 is an apocalyptic number.

It is an amenable number.

21706865 is a deficient number, since it is larger than the sum of its proper divisors (4341379).

21706865 is an equidigital number, since it uses as much as digits as its factorization.

21706865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4341378.

The product of its (nonzero) digits is 20160, while the sum is 35.

The square root of 21706865 is about 4659.0626739721. The cubic root of 21706865 is about 278.9538555854.

The spelling of 21706865 in words is "twenty-one million, seven hundred six thousand, eight hundred sixty-five".